I would suggest that you connect the speaker's terminals to the "speaker-level" inputs of the subwoofer using 16 or 18 gauge speaker wire, and then use the subwoofer's own rolloff control to set the subwoofer's upper limit of operation.

It should be set at around 40 Hz for your speakers.

Set the speakers to run "full-range" and turn off any sort of "bass management" in the receiver.

Forget about gain compensation and EQ; the subwoofer's gain and crossover controls will allow you to adjust for best operation by listening while trying variations in the settings.

Using those excellent speakers with that 3rd-rate Onkyo receiver is sort of like buying a new Porsche and then putting the cheapest tires you can find at Wal-Mart on it. Yukkkk!!

You need to get a high-quality integrated amplifier from Musical Fidelity or Creek or Arcam. Otherwise the money you spent on the speakers is pretty much wasted; you will never hear them perform as they should.

Agree with commsysman completely. The EQ settings are not really all that beneficial in 2.1. They are for multi channel setups.

I don't think that SVS sub has speaker level inputs so I think you may need to use RCA cables. That being said, you should still set the front speakers to full range on the receiver and set the subwoofers crossover at either 40 or 45 hz. I would try it at both settings and see which you prefer. Basically, the same goes for all the settings on the subwoofer. It is a matter of trying each and figuring out what you like best. It took me about 10 hours of listening to get my sub perfectly integrated.

In terms of upgrade, that is a first rate set of speakers and a tremendously good subwoofer. Your weak link is that receiver among the components you have mentioned thus far. What else do you have connected? If you share an estimated budget and a bit about your listening habits, we may be able to offer some suggestions on upgrades.

You are going to need to spend at least $6000 to make separates worth it. For tubes, you are going to need to spend more. The Musical Fidelity M6 line, particularly the power amp is amazing. You might consider the Musical Fidelity M6 Power amp with a tube pre-amp. $3500 for the Power Amp and probably the same to a bit more for a pre amp.

The other thing you would need is a first rate DAC. At that level of equipment, I would most deffinitely get a Marantz NA-11S1 network player. It has a darn nice feature set and is an A rated DAC by Stereophile. In the Stereophile review they compare it to a $40K DAC and the conclusion was the differences were tiny.

If you don't want to go to that price level, I would look at integrated amp. A really interesting unit is the Rogue Audio Cronus Magnum Integrated. $2295 and outputs 90w PC. It has won several awards and is a truly awesome tube unit. You could also look at the Jolida JD1000 at $2599. I like the Rogue unit better. Both are available from Needledoctor.

You are also going to want to look at an external DAC here as well. The Marantz NA8005 is a fantastic unit for $799 on Amazon. There are a bunch of other high quality DACs on the market. My perspective is, why just buy a DAC if I can get some other features like streaming via a network or streaming services like Spotify. I have the now discontinued Marantz NA7004 and love it.