That question is frequently asked at http://club.cdfreaks.com/ . There's also a big list of them at videohelp.com. I don't think you'll find any current ones that don't go at least 16X and do double layer. Newegg has a bunch at ~$40 for...
32 bit will work, well, in 32 bit mode. AFAIK there aren't that many programs that will only run on XP 64. I run basic XP home on my A-64, albeit a single core. I don't know if XP Home will efficiently use the second core or not.