If you just want to experiment with drivers, or any clubs really, ebay is the best place. Wouldn't have said that a few years back, but I no longer work in the golf trade, so I can be honest! Experimenting isn't a substitute for getting fitted, but it can be a lot more fun
If you go to a tournament you'll see the pros try several different drivers on the range!
If you buy something from ebay, you can try it at your leisure, in real world situations rather than on a range, and if you don't like it you can usually get your money back by selling it to someone else.
Shafts are by far the most important thing. With the wrong flex shaft it doesn't matter how good the rest of the club is, it just won't work. The difficult bit is that different brand shafts of the same flex can play to different stiffnesses! So if you can narrow it down to a specific shaft model that you like, then you're cooking with gas!
Currently, a lot the big name heads play very similarly, so if you get a shaft you like then it's possible that it'll work across a range of heads. However, if you find a head you like, there's no way it'll work across a range of shafts!
I've tested an awful lot of woods and irons, pretty much everythig on sale (and some not on sale!) and it's clear that if you pick any segment of the retail market, it's very likely that a lot of the products will perform similarly. The important thing is getting the product to fit you by getting it customised.
Golf isn't really like hi-fi, where two products of the same price can be entirely different. Golf manufacturers are at a point where they're very close to the limit of current technology. It's pretty hard to buy a technically bad club nowadays. But it's pretty easy to buy one than doesn't suit you!
If you don't like talking about this kinda stuff here, there are numerous forums, which I don't know if you've found? The ones I frequent are...
www.bombsquadgolf.com
www.golfwrx.com
www.golfopinions.com
Some of the mags have forum sections on their websites too.
Golf equipment forums can be very similar to hi-fi forums! There is a degree of snobbery in certain places, and there are an awful lot of people who have equipment for the pose value rather than it's performance! "Tour Issue" golf gear is as emotive a subject, and as hotly debated, as cables are on hi-fi forums.
Good luck!