my point had more to do w/ the fact that switching to PCI for Apple has little to do w/ power-savings or performance per-se, it's likely a combination of the factors. it likely has more to do w/ switching to a different brand to increase any degree of performance as well as making the PCI switch, along w/ powersavings. if in fact the ATI x700 or the nvidia 6600 could work in the powerbooks you'd have to address the form factor. try slicing/condensing a .4 inch of your bro's notebook abf and see how well it cools. then of course, while trying to put it into that thickness, make sure not to reduce the capacity of the battery.
the z71v is a decent DIY system, but that's what it is. there's a lot that's allowed for in those systems bc of their target market, primarily custom computer shops, and secondarily ppl buying from places like coboc. basically, the more i look at it, the more puffy it looks compared to other thin/light notebooks, IMO. but i digress. engineering such computers has much less work involved than doing something where the vendor says, "we want it w/ these specs. this thin, w/ this kind of battery life, etc" all the sudden, the equation changes. i.e.-there's a reason why the ~1" (or less) machines only come from the brand names, and for a premium.
in other words, swapping out new GPUs and interfaces for DIY geared systems is a relatively easy thing to do when u literally, have room to play with.
keeping it in the ATI family, for Macs the x700 may not be a huge step in performance from the 9700. so inevitably one has to ask whether it is worth the upgrade from a manufacturing/engineering standpoint, or whether it is better to wait for the next "9700" that allows for strong performance, battery life, and thermal limits. perhaps one of the silliest moves i've seen in some time was for the Sony S series, moving from a dated stock 9200 (BTO option of 9700) to an integrated stock w/ BTO option of the nvidia 6200 go w/ turbo crap, um, cache. personally i'd rather have the 9700, but that's me.
what is the native interface for the nvidia mobile chips? the big hullabaloo about ATI and nvidia moving to PCI was that ATI had PCI native chips while nvidia would be using AGP chips w/ a PCI bridge and PCI native cards. so is the Go series just based on AGP chips soldered to a PCI-X card? notably there wasn't any significant differences between the AGP and PCI performances for the nvidia chips. however w/ the mobile GPUs it may be different, tho it would be assinine from the standpoint of manufacturing costs to have portions of a typically unified architecture split off between AGP and PCI, as u'd noted.
perhaps most notably, while some "swappable" PCI cards have been made for high end (and brick-thick) systems, the rest of the market is still "just soldering" the chips to their mobos. this is particularly true for vendors that want their systems to be as thin and light as possible. ahem, oh shite, the PBs are in that category!