You have a really nice setup jaybird. Sleekstack is also one of the good guys here to get ideas from on some of the more costly amps and speakers. He's got a couple of drool-worth setups anyone on the site would love to have. I'm assuming you're a canuck like me and I'll try to come up with an idea or two for you but for the $$$ stuff he's really a guy to listen to imo.
I do think you may see an improvement in the 7200's if you give them a little more power because their power handeling ability is well above the 100w you're feeding them now and they have several drivers to power. Your on-board amp is only powering your 12" woofer and the radiators leaving you 4 mids and 2 tweets to drive.
I still contend that the best way to be sure more power will equal better sound is to audition your speakers with different power supplys at the dealer who sold them to you. I doubt they'll have the integra receiver (which is a nice unit but a couple of years older) but they should have something comperable powerwise for you to do your A/B testing with. Just make sure they level match the setup for you.
I do have a quick question (ok 3 of them) though, are you looking for a multi channel amp, a stereo amp, or mono-blocks? If you only have the 2 7200's then you can get a killer amp used or just an amazing amp new. The good thing about amps is that well built ones last forever. Companies like Bryston offer 20 yr fully transferrable warranty. (I like to promote Bryston because they are Canadan and one of the few "high-end" brands I'm aquainted with.)
Some good names that you'll find in the $3500 category be they new or used are Classe, Bryston, Marantz (in this price range their stuff IS good imo), Mcintosh, Anthem, Rotel, Arcam. For a few of those companies $3500 will put you into their top end products. Look audiogon or ebay for used. Audiogon members often won't ship to Canada but you'll find more high-end gear there. Also look at canuckaudiomart.com.
For used here's a few good products:
http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1162947477
http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1163023043
http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1162136696
And here's one from Toronto:
http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1162920849
Have fun and take your time. You have a good budget, just spend it wisely.