You have so many options with your Remington 700. Here are some that I've used:
AICS - Just screw it on, and it will work. It is heavy, and you might not like the ergo.
MDT Chassis - Much like the AICS, but has different ergo.
Vbull - Works really well. Need to modify your stock for it to fit, though this can be done with hand tools.
Alberta Tactical detachable mag system -- Much like the Vbull system, but faster to reload. I am told that they have newer versions that have the mag release on the side, and use AI AW mags. Big +s there IMO.
H&S detachable mag - Drop in, no stock mods needed. Mags aren't as good as teh AICS ones used in any of the other systems above.