Thanks for the info.

As long as you're not having any trouble running a 95w Q8400, you won't have any trouble with a Q9650 either.

Increase in performance might not be too noticeable (marginal), but if you use any apps that are CPU heavy or do some gaming, then you might notice more out of the Q9650.  https://cpu.userbenchmark.com/Compare/Intel-Core2-Quad-Q9650-vs-Intel-Core2-Quad-Q8400/m1706vsm1663 

In my previous 755 MT, I went from an E8400 to a Q9650.  I noticed more difference out of an SSD.  YMMV.

Optiplex 760 DT

Intel Core 2 Quad Q9400 

*Previous processor* Intel Core 2 Quad Q8400

8GB Ram PC2-6400

Motheboard 0R230R

Chipset Q43/ Q45

@Jurgis M 

@MalCriaO 

@bradthetechnut 

@Henry dell 

There is more than 1 version of 760 motherboard.

Some work with quads and some DO NOT work.

The Optiplex 760MT and SFF uses two motherboards -
T674K Non-Quad core CPU motherboard
U562N Quad core CPU motherboard  MT

M863N Quad core CPU motherboard SFF

F373D

M863N

N449H

J656F

If you have the 1st one you cannot use a quad core CPU on it.

SFF power supply is too small to support 95W processor.

38G73 E7400, 2.8GHz, 3MB, WFD, R0
F31F5 E7500, 2.93GHz, 3MB, WFD, R0
06YMG Wolfdale E7600, 3.06GHz, 3MB, 65W,
H399J Wolfdale Dual Core E8400, 3.0GHz,65W,
D923J Wolfdale Dual Core E8500, 3.16GHz, 65W,
N654J Wolfdale Processor E8600, 3.33GHz

@MalCriaO already mentioned having Motheboard 0R230R in a DT, and is already running quads.