I run a 62/HC/140 (I used to run a NAP250). Speakers are ES11s on dedicated stands.
Recently I changed sources to a CD5 and NAT5, so I picked up a NAIT5 to complete the set.
I've found the NAIT5 to be a very enjoyable amp. It doesn't have the same power as my CB boxes and I find myself turning up the volume to around 10 o'clock to get a room filling sound. It's fast as anything I've heard from Naim and very punchy without the shrill edge of the NAIT3 (had several of those, tried to love it but never could).
In its raw state, bass isn't overwhelming but it is present and articulate - not as much slam as a 250 but bass is well balanced and pleasingly full. The sound sits between the speakers in a very solid way. There's even a bit of depth to the sound stage. Adding a Hicap (or in my case an Avondale PSU) pushes the sound wider, creates a richer midrange and brings more bass to the party with pace and timing intact.
I expected to have the NAIT5 in situ for a couple of weeks. Two months later it's still in place. Overall I'd say the NAIT5 retains more of the 'house sound' of the CB/Olive era - certainly more than later Series 5 boxes.
So a recommendation from me for the NAIT5. If you want more power for your SBLs, a NAIT XS with 60w per channel and the same upgradeability might be worth consideration.