You can start with a 2.0 for music. Get a good, modest system and you could be happy enough. Stereophile has recommended components in their April and October issues. This system can also be used later in a Home Theater (HT). 

Going to 2.1 will get you smaller speakers with a subwoofer, which could be used later for HT. The smaller front speakers may have less intermodulation distortion compared to larger-driver speakers of the direct-radiator type.

Going to an AVR with 5.1 or 7.1 channels will get you all the channels you need for stereo audio and HT. Remember that some audio is released in 'surround' configuration too, and you may or may not want to get into this.

One possible limitation of AVRs is that each channel will be limited in their power output because they have to cram 5 or 7 channels into one box compared to a purpose-designed 2-channel amp. Think of five amps on one chassis and all the heat that needs to be dissipated, and you'll see why it's not likely to find AVRs with 200-watt amps for each channel, marketing claims aside.

I can't recommend any AVRs as I don't have one in my 4.1 HT setup. When I looked into AVRs, none had the power to drive my speakers well enough. I also had tweaked all my electronics, and was not inclined to tweak another six channels in a modern AVR, which would not have the chassis space for such work anyway.

The following is a description of how I setup a HT without an AVR.

I started with a 2.0 setup for music only. The speakers are good enough that a center channel is not needed for HT. I added another 2.0 amp and two speakers for the surround channels. I later added two powered subwoofers for the LFE (the 0.1) channel. All of this is sourced from a Blu-Ray player with 2.0, 5.1 and 7.1 analog RCA outputs. I left the center channel unused and set-up the player with that center channel un-selected so that the dialog goes to the two front channels. Because the speakers can reproduce the center image so well, I don't need a center channel amp or speaker.

Since the 2.0 main (front) channels is mainly for music, I have other sources feeding the preamp, power amp and front speakers. The Blu-Ray player outputs its two analog front channels into one pair of inputs of my stereo pre-amp.

The analog surround outputs of the Blu-Ray player feed a separate 2.0 amp for the rear (surround) speakers, which are nearly identical to the front speakers. The inputs to this rear amp have attenuators to adjust the level to match the front speakers without using a pre-amp.

The LFE channel of the Blu-Ray player is fed to two powered subwoofers, one cable split into two, one for each subwoofer. I formerly had one subwoofer of a smaller size. I took that out and put in two larger ones. Two is much, much better than only one, when properly placed!

All this sounds like it works well, and it does. One compromise is that there is no master volume control when using the HT mode of operation. I have pre-set the levels which produce the correct same outputs at the listening positions for HT, and it's loud enough. For stereo, the pre-amp volume control works as it usually does.

There are ways to build a 6-channel volume control between the Blu-Ray player and the other preamps and amps. I found that not needed for now.

Good luck!

I agree with "ap". i started with what I consider to be a good two channel system to which I added MC/surround capability. I also have no center channel speaker. I don't have the space for another full range ESL and I don't think I really need it. All my two channel sources are connected to my two channel preamp and my front speakers (ESLs bi-amped with electronic crossover and dual sub woofers). All my MC/surround sources are connected to my processor which is connected to my preamp in a bypass mode set up. My rear channel amplifiers are connected to the processor. My rear speakers are another pair of ESLs bi-amped with an electronic crossover and a dual subwoofer (two separate subs in one box). 

When I want two channel sound I use my preamp and the front amps and speakers. When I want MC/surround sound I place my preamp in bypass mode, turn on the rear amps and use the processor to control everything. I feel that this gives me the best of both worlds considering that I have one room and "one" system for everything.

If I didn't have a processor I'd connect things the same way "ap" has.

I think you have to decide what you want.  If you want a 2channel system (with or without the sub), there's no need for an AVR unless you require video processing and/or room EQ.  A player like the Oppo BDP-93 will handle any source disc in any number of channels and will include bass management if you want to add the sub.  Just add a good integrated stereo amp and you are good to go.

If you want more than 2 channels (and I would be the last one to discourage that aspiration), start with a choice of L/R speakers and get an AVR with adequate power for the chosen speakers.  They certainly exist for the mainstream speakers you are considering.  You can buy the additional speakers/channels when you choose to expand.  

As for the speakers, I would not worry about choosing the same speakers as owned by your relatives but you need to audition them because the ones on your list differ significantly in how they sound.  Do you hear a difference between the Klipsch and B&W?

Most of the better surround processors (at least that I have seen have pre-outs) and stereo bypass.  As such I let surround processor simply act as a preamp... and feed my various amps.

In the mid 90s I bought a new Rotel RB-980BX amp , and matching pre amp separates. These are supposedly some of the best amps Rotel built I am told in their power class.  They sold new for about 1500 for the amp and another 700 or 800 for the preamp.  Today one can find them on eBay used for $200-300.  Currently I run two bridged mono RB-980BXs for the main LR stereo pushing bi wired Vandersteens.... and two more RB 980BXs in 2 channel mode for the surrounds (pushing Original Mirage SM2.5s, and Vandy 1Bs).  The sub is powerered.  All being feed from the pre outs on the surround processor.   The abilty to balance the preouts is important too if your running differnent power for the 2 channel music than your surround channels as I am. . 

Some to thing about when you buy your Surround processor is the ability to expand to separates.

DEM