I'm looking at doing a similar kind of upgrade. Want to replace my E2140s with E5200s. 2.8/3.2Ghz to 3.6-3.7Ghz. Already bought the E5200s, though, so I should probably go ahead and just swap them. I'm just lazy, and I don't have any real pressing need to go faster.
I don't even use my Q6600 3.6 gaming rig, it just sits on my floor unused. Sad, huh?
Edit: I am using GA-P35-DS3R v1.0 mobos in these two E2140 rigs. Should I upgrade to Q9400s, or E5200s? The Q9400s would be maxed out in this mobo at around 3.2Ghz, since I don't think P35 goes much above 400, esp. on a quad. (In fact, will it be a challenge to get them to run at 400FSB?)
I already have two Q9400s.
In fact, this is what I have:
2x DFI X48 T2R boards, which I originally purchased to go with my 2x Q6600 G0 CPUs (one currently installed and OCed to 3.6, on a Tuniq Tower), I have 2x Tuniq towers.
I also have 2x Gigabyte X48-DS5 boards, for which I purchased 2x Q9400s, but then later picked up 2x Q9550s at around the same price, so my Q9400s are available.
Then, I have my dual-cores. 2x Gigabyte P35-DS3R v1.0, with 2x E2140s. Both OCed to 3.2, but the one I use as my current primary rig (and has a MagicJack running 24/7) wasn't "unlimited stable" at 3.2, so I cranked it down to 2.8. I also have about 3x E5200s, one M0, and two R0s.
For RAM, I have 2x 4GB Patriot DDR2-800, 2x 4GB GSkill DDR2-800, and 2x 4GB A-Data DDR2-800. The Patriot is currently installed into the two E2140 rigs. The GSkill and the A-Data were going to go into the two OCed Q6600 systems, but since I bought the two X48-DS5s, I figured that I could just put 4GB into each system, and forego 8GB RAM for now.
So how should I arrange these rigs? Should I drop E5200s or Q9400s into the P35-DS3Rs? If by chance the problem with stability at 3.2(400FSB) is the FSB speed, if I have to drop the bus speed down to 350 like I have it now with the Q9400s, then they will only be running at 2.8, whereas the E5200s wouldn't be limited by FSB in any practical sense. I would hate to waste the capability of the Q9400s. Perhaps I should pick up two EP45-UD3P boards too?