Most amps that have meters are so inacurate in the readout(MAC excepted) that the meters are useful only as eye candy.

Man, those old SAE amps were something!

Put "VU meters" into a search engine. You can buy add on meters for your existing amplifier. If you have a local pro sound shop, they very likely carry add-on meters in stock. You'll have to buy rather expensive peak reading meters (not averaging or weighted) to even get close to an accurate idea of how much power you're using as most meters are far too slow to be of much actual use. LED's are faster than needles and you'll want a "peak hold" feature to be able to read the maximum power output.

If this is just being done out of curiousity, you'll probably find the cost is far too high for what you'll learn. If you just want some meters bouncing around to the beat of the music, I usually suggested buying a cassette deck with the biggest meters you can find and watching that instead. It's far cheaper than good power meters and will do the same job. For the price of a cassette deck today, you might want to consider a used Dynaco A400 or Marantz 510 with meters and replacing your existing amp. Big meters - big fun!

You can also work backwards with a Radio Shack SPL meter and a bit of math. If you know the sensitivity spec of your speakers, you can figure how much power is being used by reading the peaks on the RS meter. Its response time is very slow but not any worse than most power meters you will find for the same price.

http://www.myhometheater.homestead.com/splcalculator.html

Oh, and, Tony, it's not how many watts your amp,is putting out; its how many quality "watts" your amp is capable of producing. As they say, it's only the first watt that counts. If the first one sucks, the next 499 don't count.