Aren't the things the OP is looking for from Apple, upgrades possible as a DIY option? Video card, minor speed bump (CPU swap/drop in) RAM etc.
Right, but any change in the Mac Pro could result in a substantial price drop for me, and here's why:
Normally the Mac prices in Swedish Kronor including VAT are (roughly) the prices in USD multiplied by 10. So for example the MP quad 2.66 and the MBP 17" 2.66 should cost...
24,990 SEK (MP quad 2.66)
27,990 SEK (MBP 17")
But they don't. The prices are...
26,995 SEK (MP quad 2.66)
25,495 SEK (MBP 17")
So for you guys the Mac Pro costs $300 less than the MBP 17". But if you were to come to Sweden and buy them, you would pay $150 more for the Mac Pro than the MBP 17". There's a $450 discrepancy there.
Why, because the exchange rate at the time a model is released dictates the price, and then they stick with that price regardless of currency fluctuations, until they release the next model. When the MBP price was set (November 08) the exchange rate was rather favorable from a Swedish POV. When the MP price was set (March 09) the exchange rate was abysmal; the USD was up to nearly 10 SEK. Now it's back down at 7.76 SEK. Hence the 26,995 SEK price we're stuck with since March is kind of an anomaly (same goes for prices on iMac and Mac Mini). The USD peaked in the same week that those models were introduced, then quickly dropped again.
So while any minor update to the Mac Pro line would be nothing to lose sleep over from a performance standpoint, it could have a major impact on the price.