Recommendation for speaker upgrade for main home listening and audio environment

Does it have automatic room correction/sub calibration?
If so, a Hsu V15

Dynaudio Special Forty S40 , for sale on AudioGon
Depending on how much you could sell your KEF Reference 102/2.
You could be a little bit over your budget.
Dynaudio are supposed to be good for music and Home Theater ,
according to review.

Don't want to spend more than 1k for a pair, and definitely want a decent upgrade in sound.

Save up more $$$ to do a meaningful speaker upgrade or just add a pair of SVS SB1000 subs for $1000 — that’d be a pretty big sonic upgrade and give you a near full-range system. 

I just got a pair of KEF R3. They were demos, and I paid 1400 for them. KILLER!

That's a good deal and yes they are!

Your KEF 102/2s are a real sweet, smooth sounding speaker.  If you like the old school KEF sound, it would be hard to replicate it in new speakers. I have auditioned the KEF R3s and LS50s, as well as some other new KEF speakers near your budget and I don't think they would be an upgrade over the 102/2.

If you don't mind used speakers, I would recommend any of the KEF Reference Models One, Two. Three and Four which were made between 1994 and 1999. They have the same sonic signature as the 102/2s but with greater bass extension and a larger fuller soundstage. They have a similar Uni-Q driver for the upper and mid frequencies and a similar coupled cavity bass loading arrangement for the low frequencies. The Model One might not be a significant difference compared to your 102/2 so I would look for the Two, Three or Four. These are tower speakers and the Models Two and Three typically go for under $1k.