Ok guys. I have about 300 hours on the Ref 5 SE. I guess it's run in by now. Here's my reactions FWIW.
Yeah, I think the SE version has a more refined sound presentation. Just sounds a bit smoother. Better bass and punchier -- probably because the power supply was doubled. Was it worth $2500? Sure, why not??? Is it a day and night difference?? A "whole nuther' league"?? I don't think so. Still has the ARC house sound.
Do I recommend getting the upgrade done? If you have the spare change . . . sure. If there's something else you're looking to do, and it's either option A or the SE upgrade, but not both, . . . tough call. I s'pose' it depends on what you have in mind.
Maybe I sound a bit reserved because I think I've reached the point of diminishing returns. I think I'd have to spend a heck of a lot more change to squeeze much more out of my current rig, e.g., change out my $7K ARC VS-115 amp for a $12K or $13K ARC Ref 150 amp, new speakers, and so forth.
Actually, I'm planning on auditioning a pair of Quattro Woods at a nearby Vandy dealer this week. The Quattros will be driven by an ARC VS-115 amp the dealer took in trade. I'll come back with some reactions for you Vandy fans. For some reason, I'm dubious that I'll get blown away.
I realize that some feel my Paradigm Sig. 8s are "mid-fi" speakers. Fact is that the Quattros and S8s cost about the same and Paradigm can pack a heck of a lot of R&D and QC into the S8s because of economies of scale and because they build pretty much everything in-house. That's all I'll say. Don't want to start another speaker war.
Cheers.