Sorry, I havent compared the esi 2000 to other samplers in any hands on fashion to know how its output compares. As for things coming out different then they go in, Id say thats not a problem anymore than with other recorded mediums, akais are more crisp emus are warmer.
The esi 2000 is really old tech it dates back to 1997 and Id guess some of its technology is before that. I cant give you any definitive answer on what to get except to say that I am definately not regretting getting it instead of an s2000.
The s3000 would be grerat for drums though with its 8 outputs. The esi has its upgrade for outputs the turbo expansion as well. On some reviews at some sites people are just stupid, especially with sampler. Almost every variety out there gets bad reviews simply because people are new to sampling and dont understand their machines.
If you want to read actual good reviews and ask questions at a forum where people know their shit check this site:
www.sonicstate.com
I find its reviews and forums more helpful than harmony central. Their forums
www.the-gas-station.com are by far the best place to ask synth questions that Ive found.People there seem to know their shit.
also theres:
www.vintagesynth.com
this site has lots of great info
The esi 2000 also comes with 2 sound cd's one of them being
the protozoa wich has all the sounds of emu's
proteus 1,2,3, plantet phatt, orbit and vintage keys modules.
And yes you could still use the sounds in your
rm1x with the esi. And if its easier you could also sample them into the esi if theres any strange reason to do that., Also consider assembling a dedicated cpu and using software for your synthesis and sampling. Programs like reaktor, vaz modulator, orion, reason, and gigasampler also halion can give variety thats hard to get with synth hardware unless your a rich man. Im going to get an imac and dedicate it to reaktor and also as a tag team with my g4 for wird experiments such as with metasynth.