A pair of Oktava MK012 SDCs would be nice. I've used EV RE15s on many occassions with great results.

It ultimately depends upon what you need to accomplish with the recording. The RE15s will blend the piano into a rock mix. The Oktavas will do almost anything you want, including classical music. A single Shure KSM44 in omni will capture a nice piano sound for a jazz recording...

I assume you mean per microphone?

Then a Rode NT-4 would be a good choice for a stereo microphone or a matched pair of Rode NT-5s.

You did not say what kind of piano you had or were trying to record or where or why you were doing the recording. I assume a grand or concert grand? In a Concert Hall or in a living room or rehearsal room or studio?

With the RODE NT-5s you could do a very nice job in a studio or rehearsal space but it is all in the placement and you will have to do some experimentation to see what works best. The NT-4 would be a good microphone for picking up the piano in a concert type situation.

Best of Luck!

Thank you very much for your replies!

I am planning to record on concert grand in recital halls (not studios). I am trying to make a demo recording.
Also, what would be the easiest and cheapest thing to connect my microphone to: a mixer, a computer interface (Mbox, etc.), or a harddisk recorder?
If I have an Mbox2 or a hardisk recorder, would I still need a mixer for a high quality recording?

Thank you!

if you ever have the chance use shure ksm44's. a wee bit out of ur price range but by far my favorite mic to use on piano.

I would definately record the piano in stereo, especially classical, that means you need a stereo mic or two mics. I can recommend a pair of Oktava MC012, they also offer additional omni capsules which is a nice option in good sounding rooms. Rode NT5/NT55 also have an omni option.
Regards
Hermann