What should i buy for my studio?

[JeffTD]

If you've already got good conversion and enough line-ins, don't hesitate to get some SCA preamps.

 

[Josh Burgess]

You can get the API A2D for $1400ish used. I'm pretty sure that's what I payed for mine.

 

[acappa]

I´ve recently switched from a homestudio to a more professional setup...and TBH conversion upgrade has become the key feature in my new setup, I switched from Focusrite Saffire built in conversion to RME ADI2, and then to SSL conversion. Not a big step between ADI2 and SSL, just the amount of channels...
Also I bought a Chandler Germanium mono preamp and was a night&day improvement!