I personally would sell the near stock GSR and buy a 2 litre converted GSR already with EVO upgrades and bodykit etc.
It's cheaper to buy built than start from scratch.
You never entirely get a 2nd hand modded car to your exact taste, but it certainly does save you a lot of time and $$$ in the long run.
Somebody touched on the current 2016 prices in Australia for private sale EVO's.
Here's a quick list based on minimum value for good condition stock cars (Note modifications increase value):
CD5A GSR Lancer Turbo 1.8T's go for around $5k+
CD9A EVO 1's go for around $10-12k
CE9A EVO 2's go for around $15k-$20k
CE9A EVO 3's go for around $20k+ (about $5k more than an EVO 2 of equal quality)
CN9A EVO 4's go for around $8-10k
CP9A EVO 5's go for around $12k-$15k
CP9A EVO 6's go for around $14k+
CP9A EVO 6.5 TME's go for around $22k+
CT9A EVO 7's go for around $14k+
CT9A EVO 7 GTA's go for around $12k+ (Automatic transmission EVO 7's for those who didn't know)
CT9A EVO 7 RS go for around $16k+
CT9A EVO 8's go for around $17k+
CT9A EVO 8 MR's go for around $22k+ (about $5k more than a normal EVO 8 of equal quality)
CT9A EVO 9's go for around $26k+
CT9W EVO 9 Wagons go for ???????. Import Only. Only 2500 were ever made. I couldn't even put a price on it. Say $30k+ because of the hassle!!
CZ4A EVO 10's go for around $28k+
CZ4A EVO 10 MR's go for around $30k+
CZ4A EVO 10 Final Edition 2015 models (last 1000 models of EVO X's ever built) go for around $60k off the showroom floor right now.