Going rate for a Shadow on the UK market at the moment is around £11k for a CD, £14k for a DD, and £17k for a Streak.
I'd personally not touch a DD, they are too heavy and don't offer much performance advantage over the smaller engined CD, as well as being noisier inside.
The CD, which uses a 503 engine, in my opinion is the best cheap flying machine of the three. Typically it'll take 2 adults and about 3 hours fuel, with a cruise speed of about 65kn.
The Streak however it must be said has a nicer wing to fly, being shorter and stiffer, and should give you another 10 knots in the cruise. Engine options are many, so it's really a case of looking at the W&CG and the performance for the one you're looking at.
CD published performance figures are 137m TODR, 183m LDR, 700 fpm climb, 13:1 glide. I'd double the field figures for safety but otherwise say those are pretty much spot-on. I've never seen published figures for a Streak, and the published figures for the DD are pure optimism (91m TODR !).
Unless you are very broad, the front cockpit on all models is fine, and a real pleasure to occupy. The rear is distinctly cramped, but there is a mod available extending the rear footwell, which helps a lot. Other mods available are a long range belly-tank, folding wings, and wing root baggage lockers - all still purchasable from a chap in East Anglia. This is true of all of the models. Also with all of the models, if I owned one, I'd invest in a pair of ANR headsets, they can be a bit loud inside.
CFM went tits up last year, but there keep being rumours of a ressurection, the most recent of which actually sounds quite credible. In the meantime, BMAA, PFA and a couple of specialist companies (Shadow Flight Centre at Old Sarum, and Danny Crosbie Engineering in East Anglia) are doing a fair job of supporting the types.
P