What would you use

Twl above speaks for me, too. To add a technical note, it helps if the system correctly reproduces harmonics, timbres, has pitch... Of course, a better recording helps!

...that's what i've started to realize.
for ex: i could now distinguish Yamaha from any other keyboard; I could now distinguish ES125 from any other guitar and certainly upright piano from grand.

Electric instruments can be very tricky. It may sound like a Wurlitzer electric piano, but one would be hard pressed to say whethers it's a real Wurlitzer or is it a Korg Trinity (or any other number of synthesizers) running a Wurlitzer patch? Solid body electric guitars have very little sound of their own. The pick up design and the amplifiers used are a greater determinate of the final sound than the guitar itself. Couple this with the choice of microphones and placement and a Telecaster can easily be made to sound like a Les Paul (Led Zep I & II).

Onhwy61, I would agree it can be tricky with electronic instruments. However, unless the keyboard man is a real whiz with his sampling and editing, you can still tell. With analog synths, the patches can be similar sounding but the sonic character of each will show through. If the programmer is really good, he can simulate other synths well, but nobody can make anything else do patch 33 on a Prophet 5 and make it sound the same. Oberheims, Moogs, Arps, and others have certain sounds all their own too. Of course, none of this matters if the music is enjoyable to listen to. It is just a challenge sometimes to be able to identify the instrument as kind of a fun thing to do.

Twl, if you're looking for a challenge, try picking out the number (and of course type) of pianos used in any of those 60s Phil Spector masterpieces. Personally, I can't tell, but I read that he typically used 3 or 4 at a time. I think he also used a similar number of acoustic guitars. Talk about a wall of sound.