For 6.5 Creedmoor, there is a Springfield M1A option but it won’t match AR-10 accuracy/precision/serviceability/parts supply.
Robinson Arms also has the XCR-M in .308, 6.5CM, and .260 Remington.
For .308/7.62x51, you can go with the legacy battle rifles:
FAL
M14/M1A
Hk91
BM59
Galil ARM 7.62
or some of the newer options:
SCAR
XCR-M
MDR
Tavor 7
Out of all of these just for fun/unique rifles, I would see the BM59 as a collector’s piece for range fun, and the Tavor 7 as an interesting 7.62 blaster that runs on PMAGs.
For quality of workmanship, the Hk91 reigns supreme if you can find a real one, but it won’t be cheap so probably not what you’re looking for. You can go the cheaper route with PTRs, but once you’ve had Hk, it’s hard to look at the imitations.
FALs run the gamut of quality, with not a lot of options nowadays.
Galil ARMs are collector’s pieces.
JRA is doing BM-59s off of parts kits or imports. Mags are different than M14 mags, but available for $49 per.
I like the idea of a Tavor 7 20” with upgraded parts for a fun gun. This is a 5.56 model but you get the idea: