I've heard good things about the midiman, but I use the Card Deluxe by Digital Audio Labs. DAL sells it direct for about $400 and it sounds great. Of course, if you're just doing MP3, it probably doesn't matter too much. One thing you might check is whether the midiman will capture analog audio at 24/96. Many cards which advertise as 24/96 capable will only capture analog at 24/48. The Card Deluxe does capture at 24/96. This could be important if you want to do redbook cd's. Capturing at 24/96 then allows you to do all your sonic manipulation at 24/96 before downsampling to 16/44 (standard audio cd). This helps minimize any noise inherent in the digital manipulation process. You should also consider what kind of in/out you want. The midiman might have more flexibility than the Card Deluxe but the Card Deluxe is more than adequate for most 2 channel apps.
You will then need some software. The two best programs are Cubasis by Steinberg which is great, but a bit expensive, and SoundForge by Sonic Foundry. SoundForge is also very good although a bit slower. It is also cheaper. Good Luck!!
