HPC Hardware question

Hey there,
I've got a question about computers. We're looking at buying some
mid-range computers for number crunching. I still have to get
specific details, but it would involve crunching large sparse matrices
(>2^20x2^20). The two we're looking at are the HP zx6000 (dual
Itanium 1.5G) and the Sun v480 (dual UltraSparc III 1.05G). Does
anyone have any idea which would be better for this sort of thing or
where I could look to find some sort of performance benchmarks? I was
looking at netlib.org and such, but couldn't find anything useful.
From another angle, if you had ~50K US to spend on a computer
specifically for crunching matrices, which would you choose?
Thanks in advance,
m