The spectron imho isn’t a match on the 510, I found it very whippy. I’ve had a 510 since it came out and it’s taken some stick and landed carp to 18lb so why change…well the new finishes are definitely far better and the poles don’t stick to your hands anything like the 510 does when shipping.
All your Top 4s will fit any of the Diawas as stated above. Depending on how you stretch your wallet, I would go for either the Tourny x or the Airity, the G20 may be ok at 13m but in comparison to the other two it does lose it at 14 and 16m. There are some deals about to be had and you may find some doing 0% over two years like fosters.