Hello Hlau...
Just to let you know...
The GeForce 2 MX card has no fan, and is JUST the right size to fit into your Cube (if you've managed to coax the card from a Tower user, you'll have to exchange the mounting bracket for the bracket that's attached to the existing graphics card first...). You'll probably benefit from placing a fan inside the chassis anyway - the Cube was designed as "fanless", but Apple still reserved a spot for one, and a power point to fit one internally if required, for such things as Dual-Processor Upgrades, etc... (Ha!)
The Radeon Cube, on the other hand, is a much more powerful card. A lot has to do with the drivers - technically, however, they are similar. But ATI has the jump on nVidia with Apple, so their cards do a helluva lot more. The reverse could be said for the PC arena, as the nVidia cards beat their opposition with better driver software. A recent whisper was overheard as saying that ATI drivers won't be supported in the future by Apple - so the ball is really in your court as to which card to go for.
Unfortunately, the Radeon cards are fairly rare (Damn!), because Apple took it off their store site as an accessory (product no. M8320ZM/B). And equally unfortunate is that the nice people on ebay.com know of it's relationship to HEN'S TEETH, and will therefore charge accordingly (Double-Damn!). The other problem is that it has a fan - and in some cases, a NOISY fan... depending on how (un)lucky you are...
I'm still trying to determine whether the new Geforce 4 cards (or even the GeForce 3, for that matter) will fit inside the confines of my Cube. Also, it would be nice to find out if these cards are "backwards-compatible" - if it actually matters if the card is rated for a 4x AGP slot rather than the Cube's 2x AGP slot.
Any ideas?
P.S. - I also recently read that the new GeForce 4 card won't be as fast as it's PC counterparts just yet, as it's primarily designed for an 8x AGP slot, and not Apple's current range of 4x AGP-equipped Quicksilvers...