Sure the kick in the back from a turbo is fun but a 944 (of any kind) over a 911, gimmie a break. The 944 may be faster but it lacks the emotion. I've driven a friends 944 a few times and the only emotion I felt was the longing for a flat 6 behind me. Sure the 944 is more modern and faster but I'll stick with my strangly balanced and noisy 73. My advice, put a 2.7 RS engine in the 911 take a performance driving class and stay away from water.
-zuff

Interesting thread all round. Now for my 2 cents.
First off you should check all the suspension, alignment, ride height, brake etc issues and see if that helps..... Next up the tyres. I have a 72E and recently changed from part worn but time expired Dunlop D40s to Pirelli P6000 as recommended by my mechanics, Autofarm near Oxford here in the UK. This has made a serious difference. Before this change a damp road was always entertaining, with never a dull moment.

If after all this you still feel in need of reassurance try lowering the car a little, a couple of inches should help without destroying the ride height. A few '70s 911 run like this around here, they look great and seem to find additional reserves of grip etc.

Only then should you think of getting the engine up graded, although I prefer the 'small' (under 3l) 911s to the larger engined versions. Its mainly the sound track as even the early ones are fast enough to endanger your licsene round here.....

As for getting a 951, well, its probably a better car, which is easier to drive quickly, it should be after all its two to three generations newer in its basic design. But it will not be as fun to drive at the same speeds as the 911 and ultimately not as rewarding to drive as the max. However is is better Porsche? I think that one is down to individual choice. Lets just say I prefered and early 911 and a Golf Gti (I know) to getting a 951. The Golf has since been replaced by an Audi S2 Station wagon (230 hp, 258 lbs ft, 6secs and 150 max.

I do feel I have the best of both worlds...