It works now
I'm very pleased
Excellent framerates the Debian way.
I first added the nvidia info to /etc/modutils/aliases as you pointed out and got to work:
I use the k7 prebuilt kernel, so I installed nvidia-kernel-source, nvidia-kernel-common and kernel-source-2.6.6. I then compiled the nvidia module against the kernel source of 2.6.6 and after installing the nvidia-deb I copied it into the prebuilt kernel tree.
I first installed the nvidia-glx (which unhappily also installed nvidia-kernel-2.4.26-1-386, but is left unused) and then loaded the (already present in the kernel) nvidia-agp and the (just compiled) nvidia module. Last, but not least I reconfigured X, choose the nvidia driver instead of the nv driver and unchecked GLcore and DRI.
I fired up X and thus direct rendering was present. A quick test with Armagetron made me happy. Very good rendering at 1280x1024 at 60 to 70 fps (which is much more than my previous Voodoo could handle).
Hopefully more readers find this helpful, because the several guides I found were more confusing than helpfull (noobs need straight answers, not a tech guide) and next to that, the debian modules are not completely ready. Apparently dependencies are incorrect and a package called nvidia-graphics-driver is not available at all at the moment.
I will try the drivers from nvidia some other time, for now the Debian provided packages do a decent job.
p.s. the card is a 440 anyway (oops...)