intel vt-d (directed i/o) using sandy bridge laptop

i have a few questions that i couldn't google my way around, with regards to vt-d and sandy bridge laptops. i should start by mentioning that i will be opting for a 2720-qm or 2820-qm (if prices fall) which are both stated to support vt-d. now, on to my questions.

first of all, the chipset. the laptop i am looking to buy will either be based on a clevo p151hm or an msi ms-16f2 barebone using the hm65 or hm67 chipsets respectively. is there an issue with regards to these chipsets which would prevent me from using vt-d features ?

second, the bios. do any of these two models have any bios limitations which would prevent me from using vt-d features ?

third, the implementation of pci-express graphics passthrough, that i intend to achieve with either an ati 5870/6970 or an nvidia 460/560 card. is there a difference in how well each of these cards perform with vt-d graphics passthrough under xen virtualization ? i have read something about the way nvidia implements certain features in their cards which can cause conflicts with vt-d but the source was a couple years old. still, for example, parallels is not giving support for this feature except for a select few quadro cards, which seems to support this case.

finally, some background information. i intend to use dual monitors, hope to do some graphics work / gaming on windows 7 as guest on the xen hypervisor under linux or using xen bare metal while running windows and linux as both guests. frankly i am sick of dual booting and i've seen some recent demonstrations on the interwebs giving me some hope for near bare metal performance with the implementation of vt-d.

thanks.