VSR-10 Revitalizing Help

Hello everyone, for the record this is my first post. I could not find the introduction thread so please, don't yell at me to go do that :/.

First things first, for Christmas this year I'm looking to upgrade my TM VSR-10 Clone (JG-BAR 10) even further.

As of right now, it is stripped completely. I have a 6.01mm inner barrel, stock hop-up and a firefly bucking. Stock cylinder with an ASGI Piston and spring guide. Running a 190 spring and a zero trigger. (Over a years use, no wear to the zero trigger whatsoever)

Since my main question was answered, from looking above, and not going down the long dark hallway of PDI parts, what should I upgrade?

-> Bumping down to an M150 Spring, Purchasing a (new) Stock Hop-up since I just broke mine.

I also do not like my stock receiver and wish to upgrade that too. If I do purchase the PDI receiver, will my stock outer barrel fit it?
Sub question -> What is the difference between the two? http://www.airsoftatlanta.com/PDI_VSR_10_Receiver_p/65333.htm and http://www.airsoftatlanta.com/PDI_VSR_10_Bore_Up_Receiver_p/65390.htm

If you have any questions regarding my research, could you please ask because it may help and finalize my decision.

Thanks, iKontradiction