Jim Brain's uIEC is probably the best bang for your buck, plenty of games can be run directly from D64 and there are utilities to get D64s of the tougher games back onto floppy.
http://www.jbrain.net/products/uIEC%7B47%7DSD.html. There is also the 1541 Ultimate available (hard to get but is something like 100% 1541 compatible) and the Chameleon is supposed to be out soon, but both of those options are quite a bit pricier than the uIEC.
Biggest cost of getting a PAL C64 will most likely be the shipping, there aren't too many up for grabs in the US so you'll probably end up having to import one yourself. The differences in compatibility on the C64 PAL and NTSC versions aren't nearly as much of an issue as they are on Amigas, the only thing I've run into issues with on NTSC units are demos to work only on PAL machines. Games are much more forgiving.
Either way, 8 bit stuff is way cheaper to get than Amiga stuff, if you stay domestic you can definitely get a whole setup for less than $100. The biggest thing you'll want to look out for is if you're buying on eBay, make sure everything is tested and working. There are a lot of dead C64s and drives around.
edit: Regarding importing a PAL C64, you could probably save some shipping if you find someone just selling the board and swap it into a locally-sourced case.