Another way to look at it is, and all this is, is, another way to look at it: how many modified TRL CD players have you seen for sale on this site? I'm a pretty regular Audiogoner and I have only seen one.
I sold my TRL Sony 595 pretty quickly when I moved up to the TRL Marantz SA14.
Yes, the TRL units used are a great value.
Like any modded unit, though, the seller takes a hit.
As for an A/B of the SA14, I have a buddy who is assessing his SA14 right now before he sends it off to TRL. Many have heard before and after. TRL can certainly provide you an opinion on what they think the difference is; but you likely will prefer the report of an end user like Oldpet, Jes45, etc who visit here often.
By most reports-the mod allegegly addresses the thin-ness and digital hash especially of the unit, while increasing detail and extension significantly.
I had mine shipped directly to TRL for the mod.