Old and New Naim sound quite different IMO, and having done numerous comparisons between the two when I 'came back' to Naim some years back, without exception, I preferred Olive - put simply, I find it more musical and less Hi-Fi sounding, and I've never heard it sounding bright, hard, let alone nasty (yes, my hearing's fine, thanks!
) . Others, clearly, disagree, which shows, yet again, that only the individual can decide what's right for them.
In the OP's case, I'd be trying some other sources (If improved musical performance is the goal, rather than a current lack of power being the 'problem'), to see if he finds much/any difference between them, and then look to amps and/or speakers if necessary.
As for Olive Naim pre/power recommendations for an initial trial, I'd say 72/140 (if you can live without RC, and no need for a Hi-Cap
) or 102/140 or 180, if RC is a must.
In terms of power amps, a 250 is much better than 140/180, IMO, but this requires a pre-amp PSU; however, there are some who prefer the non-regulated amps, so another case of trying for yourself and finding out which, if any, you prefer.
As for 'Olive 160s', IIRC, Naim did offer 'conversion kits' (I'm going to regret using that term, I'm sure...
) or some such for some CB boxes?