Zero problems with any of them, and I've had them for years. The 300s are beasts; really plenty of power. Audiosource isn't what I'd call a top tier manufacturer, but their stuff is underrated IMO. Yes, the 300s are pricey, but I got one used for a ridiculous price and the other brand new on clearance for an even more ridiculous price, so they can be found. Sorry, I didn't see that that amp200 was used. Refurbs are OK if you get a warranty with it.
I have heard good things about that particular Onkyo from Seth=L here, but when looking for amps they wouldn't necessarily be top of my list. I thought there was someone on here selling one used, but I don't see the listing.
If you can stretch the budget, the Emotiva UPA-2 is on sale for $349 shipped.
I'd actually look used also, craigslist in your area if you are in a larger city. Marantz monoblocks (MA500s, or MA6100s, both THX cert) can usually be found for $100 each.
This might be of interest too:
http://www.accessories4less.com/make-a-store/item/ONKM282/Onkyo-M-282-Premium-2-channel-Amplifier-2-X-125-Watts/1.html
Refurb 282. I've bought from them previously a number of times too. Full warranty.