For the best quality , I'd suggest you consider an external USB interface having numerous inputs and outputs including MIDI. Have a look at the Sweetwater site for MOTU and RME. You might look into Pro Tools which has become almost an industry standard made by Avid, partly because Avid is an industry standard for video editing.
The external interface will give you the highest quality ADC/DAC, the best controls, and the greatest flexibility. You may also consider a USB effects module, though today there are reasonably good software effects.
If you're recording in a studio you'll know about microphones and microphones preamps- that's a whole world of complex, subtle decisions.
In partnership with all these things is having a very good monitoring/editing software and I'd suggest Avid Pro Tools 10 or Cakewalk Sonar X2 Producer. The software effects included with Sonar and plug-ins available are very good.
If you're doing HD recording, the right computer is essential, and is a workstation configuration, not a gaming computer. I'd suggest a Xeon CPU, a healthy amounts of ECC RAM with the lowest latency you can find, an SSD for the OS/Applications, and a very large amount of storage on 6GB/s mechanical drives in RAID 1 to have a copy of everything. The video card need not be a screamingly fast one for sound, but sound work is a realm where multiple monitors (23-24" is a good size) are very helpful. If the same computer is to be used for video editing, the video card should by a very good one with a big memory and I'd suggest a used Quadro FX5800 (4GB) or Quadro 6000 (6GB), 27" 2560 X 1440 monitors, and triple the amount of HD space.