I have the 2x2.8QC as well (early 2008) and it's still "wicked fast" even with 4GB RAM only, really nice daily driver running 10.8 just well, could only use +4GB more RAM wich i just haven't got around upgrading.

MacPro's are great if you need the disk space, they have four slots for HDD's (for me, it it means less USB -drives around).

Take it, you won't regret it.