This is a great topic. Can anyone chime in on difference between these bargain tube pres and what I consider mid-priced units, that cost ~$1000? This category in particular seems kind of tough to get big bang for few dollars.
Quality of parts used is a big one. Even with DIY, $20 coupling caps, Caddock/Holco resistors and fancy RCA jacks add up quickly 
for the $1k range, find a used melos sha-gold-r; hard to beat at more than twice the price. unless, you find a used melos ma333r...

doug s.