Well, the 2510 is back in its box. After quite a lengthy session with both amps yesterday, and much PITA swapping between both amps, the conclusion was fairly straightforward. While the Exposure is a fantastic device, there just isn't enough 'extra' to justify the additional cost.
My initial thoughts stand, at least in my set up (ND5 XS2, Apollo-R, Talisman 2). The Rega has more soundstage depth and width. This quality is more noticeable on tracks that have the greatest sense of space engineered into the recording but it's there. By contrast, the 2510 deals a smidge better with absolute bass authority, seems to have a tiny bit more 'grip' without the iron fisted control my old 3010 S2D used to have.
Many pro reviews will wax lyrical and brand the Rega as 'dynamic' and 'musical', the 2510 as being the epitome of neutrality. The luddite in me can't really segregate these opinions into meaningful experiences to be honest. Both amps sound superb in my humble view, either will be a fine addition if you're looking for a quality integrated. The price difference at RRP is hard to ignore though.
Apologies if my comparison conclusion appears a tad lacklustre, I have a massive fondness for Exposure and did wonder casually if there was going to be a night and day epiphany but the plucky Rega puts up a very good fight.
Finally on the subject of build quality, even with a perfect Exposure, the Rega wins, my example is properly solid and very well screwed together, the input lights are amusing though, looking down at the amp powered up makes it look like 2 lights are lit at once, looking at it from eye level, only one light lit. The demo Exposure I had wasn't the best I thought, one of the feet fell off ! More intriguing was the sticky volume control that would not operate past 12 o'clock with the remote and had to be manually moved past this point, I'd make a point of checking this if you were buying. The aluminium casework of the Exposure seems better than the 2010S2D I used to own which had a quite rough texture, the 2510 seems a lot smoother.
Fine amplifiers, both of them.