I gotta say, these two brands are quite different when it comes to their approach to sound reproduction.
Assuming we're comparing similar priced sub-5k Odyssey gear to sub-5k Naim gear, this is how the two brands stack up (in my experience):
Naim posesses a grungier sound. The treble will be more accentuated. The presentation will sound more 'in your face'. The midrange will take on a slightly warmer color, and the bass will have this masculine, almost over-driven yet still controlled nature to it. Naim, in short, has a very distinct signature. Whether or not it works for you hinges on personal taste and associated gear.
A Naim amp paired to a Classic Spendor is a very safe match. However, Naim and the current array of Spendor gear is less of a foregone bet. Spendors non-classic line is quite a bit different from the distinctly warm and 'safe' sounding products of yore. They ain't your dads speaker - that's for sure.
Odyssey Audio gear, on the other hand, is going to sound more refined, balanced, cleaner, and more dynamic than Naim gear at the same price. While it won't have quite the same "pizazz" as the Naim gear, I think Odyssey equipment forms a better match with a wider variety of speakers and thus makes for an easier recommendation most of the times. Which brings me to Odyssey Audio and Spendor.
If you have a pair of classics, then I'd actually encourage you to try the Naim first.
However, if you have non-classic Spendors, then I think you'll be better off with Odyssey equipment. Especially given the drivers that Spendor currently uses and has been using for the past 5 or so years.
Anyhoo - that's just my long-winded take on the situation.
