I've had the Fluance SX-HTB set + SV-6 pair since June. I'm very happy with them. My only complaint is that the center channel is not matched to the mains, but they're coming out with a new center sometime this year that will math the SV set, and thus the SX-HTB mains. I started with a dayton sub and have since upgraded to an SVS PB-10. I'm powering the set with a refurbished HK AVR-325. Not only does the Fluance set sound very nice, but it looks awesome too. The pictures online don't really capture how nice the "finish" looks.
Here is one of my room pics that I think is closer to how it looks. I think on Fluance's site it looks really washed out. There's other various pics of my room in there somewhere... maybe there's an even better shot.
If you're on a really tight budget and want to go with Fluance, you might want to look at sherwood receivers. I've heard good things about them, even down to the $120-ish 5.1 model. Maybe a refurbished onkyo from ecost? Spending more on speakers produces better final sound than spending more on electonics.
You might want to add a sub to the mix too eventually. The mains are pretty good on upper bass, but die off very quickly at about 40hz if I remember correctly.
This subwoofer (Dayton Tiny Mighty) goes on sale for $99 or $109 fairly regularly. It's really a nice sub for the money, better than most offerings at best buy etc. that they sell for $200.
So.... $300-ish for the SX-HTBs shipped... I forget how much shipping was (box for the mains is like 75 pounds and frickin huge) + cheap receiver for around $160 + speaker wire, cables etc. for $40-ish = $500
I think adding a sub to the set added a lot. Maybe wait until the dayton goes on sale and pick it up for $99 + shipping + sub (rca) cable eventually....
If you don't want to bother with all that, I agree that onkyo makes some very attractive sets for your price point. I think you'd get more for your money with the Fluance set, but I admit it's a lot easier to just get everything together and have everything you need... plus you can demo it at circuit city or wherever.
I wouldn't discount Mwilding either on the rocket tyke set. Rockets are nice speakers and would definately sound good. You get a nice receiver with that package too. It would probably get you bonus points with a wife/so too since they're small and cute heh. Small but they'll back a nice bunch too.
I think you have 3 really good options here and would be happy with any of them. There's a large area of AVSforum deditated to HTiB sets that you might want to take a look at.
edit: I just remembered outpost.com was having a sale on their cherry finished polk speakers. It looks like the R50s are back up to the price of the Black ones ($199 each instead of $99 each). R30s are still $60 each and R15s are $50 a pair. If you live near a Fry's (that's the B&M right?... I live in WI and no Fry's anywhere) you might want to see if you could demo them. Too bad the R50 deal is over, but maybe R30s up front and a couple sets of R15s for a 6.1 set (no center channel deal). That would run you less than the fluance set, and especially save on shipping if you could just pick them up. I'm not really sure how the outpost.com vs. fry's works, so forgive me if I have it wrong. If you could get that set for that price + tax you might be able to sqeeze in a receiver and an on sale dayton sub for just about $500. I haven't heard the polks, but it would certainly be easier for you to demo them than the fluance set.
I would recommend trying to listen to speakers before you buy them. We can recommend stuff all day, but if you don't like how they sound it doesn't matter what other people think.