Since you like the XR6T so much, have you looked at the G6ET ?
Or here's another thought for you, if you want a decent V8, something that will go up in value and is already building a cult following and is a fantastic car to drive then have a drive of a Ford T-Series. A T3 TE50 or a T3 TS50. They are a 2002 model but a bloody great car, But make sure it is a T3 and not a T2 or a T1. The T3 is the one that has the 5.6ltr stroker engine.
The T-Series were not a production car, they were made to order and as such only 204(90 Auto, 114 Manual) T3 TE50 and 224(152 Auto, 72 Manual) T3 TS50 cars were made.
These things have a hand built 5.0ltr engine that have been stroked to 5.6ltrs, balanced and blueprinted and use an all new nodular iron crankshaft, GT40P ported cylinder heads with high performance YellaTerra springs and valves, Argo billet machined connecting rods, ACL lightweight pistons with fully floating pins, a revised camshaft profile, an 82mm diameter throttle body, a very unique three-piece high flow inlet manifold cast and manufactured by Morrison Motorsport and a Mustang conical air cleaner with dedicated mass air flow (MAF) sensor.
Following in the tradition of Aston Martin each stroked engine carries a build plate signed by the Tickford engineer who worked on it, signifying craftsmanship that goes further then any Tickford enhanced engine.
Exceptional braking is provided by a package consisting of 329mm vented and grooved front discs with twin-piston calipers and 287mm grooved rear discs.
An optional Brembo brake package is also available, featuring massive 355mm cross-drilled and ventilated front and 330mm cross-drilled and ventilated rear discs, all with four piston calipers.
Power figures are 250kw and 500nm, its not so much the power and torque that make it a great car, But the way the power is delivered and the responsiveness of the engine. It has a very flat torque curve making it a real hoot to drive. You really need to drive one to appreciate it.
Check out this Ford clip:
http://www.youtube.com/watch?v=6UJ8uDMS34o
Some info on the T-Series:
http://tseries.110mb.com/main.html
And this is me at Deca:
http://www.youtube.com/watch?v=lfY-R6mHVEQ
http://www.youtube.com/watch?v=wg_07mXCxvU
Me again fooling around on the skidpan:
http://www.youtube.com/watch?v=WDdHk9Y1ehE
It really is a great car, so if you're looking for a fun V8 definitely take a T3 for a drive, nothing like an XR8. But if you would like a Turbo then you can't go wrong with the XR6T or a G6ET.