You cannot go to 16 gig. 8 gig is possible but only with compatible non buffered non ecc non registered LOW Density Ram. DDR2 is dying or gone from the retail channel. If you get a used Precision T3500 which uses DDR3 you will be more likely to keep it for a few years. The max ram is the same as precision 380 or XPS400. You have 4 slots so 4x 2 gig is possible as well as 4x 1 gig. You may find a Precision T3400 with 4 gigs or more of ram is the same as the cost of buying 8 gigs of ram alone.