PDI makes very good upgrade parts for TM-L96s and VSR-10s. In my opinion they're slightly better than the laylax stuff. However the difference is minor.
I think you'll get PDI stuff slightly cheaper than Laylax stuff from PDIs distribution site here.
http://www.x-fire.org/top/vsr10.htmlThe Raven cylinder sets and Raven barrels they have on PDI site are very good and much cheaper than the rest of the PDI stuff. I think it has something to do with the manufacturing process or the materials but I'm not really sure. There was a big article in a japanese airsoft magazine which compared many different tightbore barrels and the Raven one was one of the cheapest and performed the best out of all of them.
You should consider getting a JG-Bar-10 from another website instead of the TM VSR-10 because by the time you upgrade it for 500fps you've swapped out almost everything internally anyway. The only differences would be the external finish and the hop chamber (which can be replaced but doesn't really need to). If you get a Bar-10 it will be a higher stock fps so you'll have a more practical gun out of the box. The TM VSR-10 would for you essentially be a quiet, single shot M4 sopmod.
I'd get the gun first.
Then a single PDI piston sear and a spring (The other sear with only last a few months tops).
Then the upgraded new trigger unit and piston to match.
Then later on get a tightbore barrel and a new cylinder set.
Or you could buy it all at once and be a total baller.