Shaken, and not really stirred...
If maint'/service costs are a notable concern, a late-model Aston Martin isn't the vehicle for you.
Anyways w/ that said, go w/ an '08+
V8 Vantage & call it a day. Yes, '06-'07 are more inexpensive as well as initial nosebleed depreciation more-or-less done w/, but they have some quirks/gremlins which have been sorted out w/ the '08+. The '08+ is also notably improved in other aspects. Prices & selection should be rather attractive for these, w/ many 2 & 3 year leases ending as of late.
Remember, even if a pre-owned DB9 is ~$80k'ish now or pre-owned DB7 is ~$40k'ish now, the former is still a formerly ~$160k+ car warranting the attention (maint'/service) of such a price strata; likewise for the latter, a formerly ~$120k+ car demanding the due diligence of such a price-point. And neither has any semblance of appreciable reliability/dependability (relatively speaking, but of-course).
And this breaks my heart, as the DB9 has been one of my "IT" cars for many, many years. But, common-sense & conventional wisdom both point to the V8 Vantage (for most individuals of respectable means/expectations) - and the '08+ V8 Vantage even more-so.
So, my best advice would be look into a well-sorted '08+ V8 Vantage, perhaps one w/ an extended warranty, obviously along w/ near bottomed-out depreciation (based on '06-'07 models, you can actually accurately predict how much & for how long it'll drop in value before it levels off!).
G'luck, these are all uber-gorgeous rides!
i wouldn't mind having the db8. i surmise that its' reliability would be satisfactory since it shares the powertrain with the new jag, i believe.
You mean the latest/current Aston Martin V8 Vantage? If so, that makes two of us!
The '06-'07 4.3L was loosely based on the Jaguar AJ-V8 architecture, but it has dry-sump lube' & unique cylinder block and heads, crankshaft, connecting rods, pistons, camshafts, inlet and exhaust manifolds, lubrication system, and engine management. Also, it's hand-assembled (in Germany, alongside the delish' V12's). The '08+ models got a 4.7L which is quite robust, to say the leasts. . .