First off, there is no corelation between a Silix 6538 and the genuine article, so I don't even know if a Sternkruz T-17 will do you any good. Next, you need to get a decent set of digital calipers, like the $10 ones at Harbor Freight. Measure your Silix crystal and maybe compare it to the CousinsUK Rolex crystal chart and see if it's similar to any of the popular crystals they sell. I doubt they sell a T-17, because it's very rare and outdated. Keep in mind that the chinese crystals are just made for these reps so they rarely have any Rolex equivalent.
If you follow some of the people who mod these Silix type reps, the key is to accept what you have and try to age it accordingly. Age the bezel insert, install a decent pearl, soften the case and scratch it up, age the dial and hands. Check out what Donerix did here:
http://repgeek.com/showthread.php?t=144934