There are actually three different Naim "lines", and if you search ebay or visit the site mentioned above you'll definitely find pics of the older two.
The oldest units have a black face and chrome highlights. I believe they stopped making these in the late 80's.
In the 90's, Naim went to an olive/black theme, and as you've noticed some of these are half-width units. In this line, the 62 and 72 preamps are half-width, and the 102, 82, and 52 preamps are full-width. All but the 140 power amp (which is also available in old chrome/black style) are full-width amps. Some external power supplies, tuners, and crossovers also come in half-width.
Of course, you'll be able to see the newest line on the Naim site.
If you're just wanting to see what the Naim sound is all about, there are cheaper ways than the Nait5, although I've heard one and was quite impressed. The Nait2 and Nait3 can be had pretty cheaply, but a better (more upgradable) setup in your stated price range would be a 72/140, or 72/180.
Don't worry about the non-standard plugs, as you can buy an adapter interconnect from every Naim dealer. I use a Chord interconnect to hook up my non-Naim cd player, but my next upgrade will be to a Naim CD 3.5.
I believe that used Naim gear is an absolute bargain right now for the sound quality it produces.
Good luck!
Graham