How useful is outboard ADC?

[res07njc]

Hey guys,

I'm new here, as a matter of fact I'm new to MD. I recently got myself the RH10 and I look foward to years of faithful service (crossing my fingers!). I originally purchased a MD to record my own guitar playing, backing tracks, etc., but I soon saw so many possibilities! In my internet research I've noticed some folks using outboard A/D converters. The sound samples that I've heard (through my Grado's) were stunning. Now, what I'm curious about is whether this was a product of the ADC or synergies between mic, setting and equipment. Interestingly, I've also noticed a huge range in price, from the $50 Parts Express unit (sans preamp) and the $400 Core Sound unit w/ preamp. I'm not really hung up on the preamp per se, I like experimenting with JFETS, but is there a big difference between these units, and the outboard ADC in general? Would everybody get one if they could afford it? Is there a law of diminishing returns in this situation?

PS: I can't wait for Big Head Todd and the Monsters to come to town!