I'm out of my comfort zone here hence this post. I've been asked by the widow of a very young shooter who sadly died suddenly to sell his boxed FX Tactical Compact PCP rifle. It came into me early last year for the new owner to collect then shortly after he got ill and died. It has a Huggett mod, Hogue AR style adjustable folding butt stock and hogue pistol grip, Optisan (MTC) 4 -16 x 44 EVX i scope which I could sell separately if necessary, and if you don't want the mod I have the AX shroud cap and like I've said already it's boxed although box not shown in pictures. I also have the charging whip and adaptor. I know what all this kit cost's new but so seldom do you see one used I could use some help with a gun valuation please. It seems to be a very high tech piece of kit with everything being tuneable, hammer pre load, reg, and velocity etc. Most of this goes straight over my old head so would greatly appreciate an estimate...Thanks. Pictures below.

https://flic.kr/p/2nXB6cE
https://flic.kr/p/2nXvJ6L
https://flic.kr/p/2nXvJ2C
https://flic.kr/p/2nXAE8d
https://flic.kr/p/2nXvJ2T