TL:DR is a 45 degree sear ok for M150 spring (500FPS)? Also name me a good bucking?

So I have recently acquired an ARES WA2000 and while a lovely looking rifle its performance is a bit on the lacking side.

Its FPS is about 380FPs on .20g BBs and whilst i know that FPS isnt the end all and be all i would like to up this to most of my sites max FPSs.

As for range i cannot tell what its like but looking at the crap bucking put in their by ARES its probably going to be pants at best, i plane to change this anyways.

So for those that dont know i have done so of my own research into this gun and found the following was compatible with VSR parts:
Inner barrel measured to be 500mm in length, needs to be a bridged window barrel.
Hop up bucking
Cylinder head
Piston Spring
Spring guide

Now i must point out that the trigger is a 45degree trigger, i read in various forums that the 45 degree trigger cannot be exchanged for a 90 degree one so i am stuck with 45 degree and it looks like the Ares one is made of the usual airosft pot metal zinc diecast material when i took it apart the last time.

So my plan is to buy a full upgrade set Cylinder head, Cylinder, Piston, Piston Spring, M150 Spring and Spring guide. I am hoping the 45 degree sear can be swapped with a TM compatible steel one for great reliability but will it be ok for an M150 spring? Also what would you recommend as a good bucking, i have heard Maple leaf being thrown around amongst other brands.