eh...Infinity's are too overrated! i have infinity 6x9's and i don't really like them. Yea...if u have a couple of hundreds to spend, i suggest u get a pair of 6x9's as well as 6.5's and power them with a 4 channel amp. Boston's are hella good, but it's costly. Pioneer's are so-so. Like if u don't have that much cash, pioneer's are good enough. I think polks had a good sound.
Just remember that at most places that have a audio sample area, remember that they're powered by amps. So in other words, it's not gonna sound exactly the same way in your car unless you have the same HU and amp.