Blimey, you're doing well for your £3k budget.... (they do make a wonderful noise)
Buying a new Trident or CB650R is where I started and thought it would be the inline four that would excite me most. That's why I wanted to consider older inline fours, for their raw nature at a good price.
I went out on the CB first, it was very nice, refined, smooth, and fun at the top when you're there. Eclutch was actually very nice but I'm not sure I want to swap back and forth between this clutch and the standard setup on GS.
The Trident was fun, very much sat on top of (felt more 'in' the CB), very light and nimble, goes where you point it. I came off thinking it was fun enough, but then so is the GS and the Trident didn't make me feel I was missing much from not having a smaller bike. It didn't feel special and I didn't feel like it could be something I would keep and cherish 'forever'.
I wanted to try the 765R but they didn't have a demonstrator, so I took out the RS and boy the experience really came alive! I felt 'connected' to the road in ways I can't explain. It was absolutely 'planted' and you could feel everything, in a good way. It's razor sharp and inspires confidence, with power everywhere. It was easy around town and in traffic and still had me smiling doing so, but the sound when really opening up that throttle and shutting it off is an absolute hoot! The quickshifter is sublime in all instances.
For me, the 765 Triple still has most of what the CB's inline-four delivers at the top end but it gives it absolutely everywhere. Way more smiles for me and a bike I really felt connected to. The perfect complement to the GS for summer fun and quick blasts.
What I don't know is if the R would do exactly the same for me, but I suspect it would. I know my abilities would never permit me to ever get close to using the R to its max, so the RS seems unnecessary, but the manufacturer option extras that the used stock bike has make it very tempting, and the ohlins on the rear felt great, so too did the brakes. I think this is why I felt so connected to the road.
But you're right a long way from a 2000 plate, £3k bike.