Seriously..... I just swapped my speakers last weekend. I changed from a couple of B&W's CDM 1's to a pair of DIY-speakers, and the guy who built them, knew his trade. They are potentially much better than the B&W's, but in my room, with my amp, there's too much high. So just this weekend I traded my amp with another guy. We agreed that if one of us wasn't happy with his new amp, we'd change back. And it worked, since I didn't like his amp, and we swapped back.
I'm happy I did this, since it gave me a clear idea of what kind of amp I'm looking for, and it didn't cost anything. Well..... some time and I made about 40 miles, that's it. But you gotta trust the guy you're swapping with, check the gear he's offering and try to get his (real!!) adress before leaving your gear with him. And make sure you can get your equipment back of you don't like his. The downside is he might want his gear back and you wanna keep it, but then you know what you'll have to save up for.....