I'm interested in upgrading to a higher end coil shock and was curious if anyone has done this already?

I called the manufacturer/importer for BMC and all the guy told me was to get a shock with the same specs (length and stroke) as what I have now and I should be good to go. He even sent me the specs, which was nice of him but I already had that info.

I mainly interested to know if any coil shock w/ resevoir will work.

BMC Superstroke 01 (2007 model)
8.5 x 2.5 (length / stroke)
Currenly has a Fox RP2 air shock.