CPU upgrade comparrison

[eyeland]

(Please bear with my eternal ranting
I am always on the lookout for small and relatively cheap upgradeprojects for my gear and thus I've been doing alot of forumsearches and post around the CPU upgrade topic.
For myself and for others in the same situation, I'd like to device a very simple hieracical list of pros and cons of the different upgrade paths.
Like many others, my T61 is very dear to me and while trying to postpone my future W-series investment, I am always scouting for priceconscious upgrades (SSD, RAM,, LCD and CPU)
A few years ago I got a defective T61 (broken LCD) for free and in time it turned into my most dearest possesion after a few upgrades (momentus 5400->7200; 1GB ->4GB ram, Broken wxga->compatible wxga+; Middleton Bios; Pcmcia eSata) At the moment, I am awaiting delivery of a few dirtcheap parts from ebay (1GB ITM + Pcmcia-CF converter for readyboost)
The point of this long introduction is that I have now persued all the nobrainerupgrades as well as the latest cheap experimental ones and I now face a few harder ones, CPU, SSD and 4->8GBram. SSD is an obvious choice as I can use it in my next thinkpad but I am waiting for a 3.Gen Vertex or intel disk to come out, hoping for 2. GEn prices to drop. I will go for 4GB ram modules at any given time when the starts align again And thus the current question on my mind: CPU (Note: I am willing to further mod my bios for a little OC/UV)
I am looking at a few different refurb, ES and new CPUs on ebay and on my local danish 2.hand site.
T7500(used) ~100$ - X7900(refurb) ~155$ - T9300(tested) ~120$
Whereas in this example, it seems pretty clear that one would favour the X7900 over the T7500, there are many cases where the choice is less clear, especially when moving between the T9xxx/T8xxx/T7xxx.
So, would it be plausible to compile a general list to make the CPU upgrade path more clear?

[RealBlackStuff]

Why waste money on the CPU? You got a very good one as it is!
Instead, spend that on more RAM or an SSD, much more effective!

[eyeland]

In general, because I was tempted by the fact that a Used T9300/X7900 is cheaper than 2x4GB DDR2 and because sometime I need someone to tell me: "NO!"
In particular, because I use my T61 "as a concert instrument" when playing Ableton Livesets/DJsets/(and VJsets in the near future).
To this end, it seems that neither more RAM or a faster disk will do much in terms of handling Synths, effects and virtual instruments. (I might go for a DYIVidock solution for VJing and 3Dstuff but it seems I need more CPU headroom for all that reverb etc. (If only the vast resonating space in my head would do, but alas, I will leave beta-testing of skull-modding to others;))

[eyeland]

After a little more ebay research, the choice stands between X7900, T9300, T8300
The price is too identical for that to be of any significance.
I assume that the key difference to considder is the balance between performance and heat where I assume that these 3 increase in both performance and temperature in the order T83->T93->X79?
If the X79 doesn't run Too hot it would appear that it is the obvious choice (unlocked multipliers as well as full sensor compatibility)?
Unless I am missing something

[techweenie]

Having personally used a T7700 and T8300, both 2.4GHz, I would highly recommend the T8300. It is a Penryn and therefore runs MUCH cooler, to the order of 20 degrees or so. It is also noticeably faster at some tasks, especially in multimedia. At the time I purchased my T8300, the price for a T9300 was absurd, and benchmark comparisons showed very little benefit to justify nearly double the price. As for the X7900, the fact that it is unlocked will do absolutely nothing for you. It is not possible to adjust the multiplier on thinkpads, at least as far as I know. It will also run quite hot because of the significantly larger die size than a Penryn. As noted in my signature, I already have 8GB RAM and a very fast hard drive, yet the single most beneficial upgrade I've done was get the T8300.

[eyeland]

Ok, I understand that a bios hack would be needed in order to do any kind of OC on the T61.
In the meantime, I was offered a T8100 for 30$, think I am gonna give it a try.
I know that I will not get a big performancegain, but running cooler would be nice and it's a cheap learning experience.
Next upgrade will be 8gb micronram and an x25 or a vertex 2 when the prices drop a little further
Cheers