no, i know that the "T" stands for thousand -> 700,000 thousand triangles

SO the 700,000 triangles slowdown your old pc system...
my system is also old (2004). 3,4ghz singlecore, 1024ram, ati radeon??? i don't know anymore . But my pc calculates the 500,000 triangles without any problems. My notebook, is the slow system.
about 100,000 triangles, and a can stop sculpting. With 1 frame per 10 seconds it took all the fun you have with sulptris....