Yep. Basically that's what I'd like to do. I just want some options for recording. It would be nice to record dry but I need to hear effects at the same time.
The setup I describe uses a mono input for guitar, (which gets recorded dry, but you don't hear it) and then a mono output which goes to the effect box. The effect box then goes into the computer where you hear it.
So you hear what the effect sounds like but you don't record it, only the dry guitar.
But in looking at the 1212m the only two outputs are used to run the monitors or headphones, which I guess would require a mixer or amp.
So the only way I could see to do reamping with the 1212 is if your effects box has Digital I/O or you have the extra I/O from an ADAT converter.
I don't think a soundcard puts that much of a load on the computer, I think it adds horsepower. You can add hardware based VST effects in your sequencer that the sound card does with no load on the CPU.
I also wouldn't sink any money into this machine, just save up and use the machine as best you can, the card should help.
Sounds like your talking about a midi controller keyboard, I thought you were talking about a synth. The controller keyboard doesn't generate any sounds but it could trigger them if you had a soft synth/sampler or an external sound module. You could make up a part that you like with the keyboard then record it and shut down the module if it's putting too much strain on the cpu.
Just have to do some experimenting...