I'm in a similar situation to you, though i am doing it in stages over next 6-9 months. Hoping to be at 500bhp ish.
Fit HPS intake with AFE panel filter-done
Fit H+S cat back system
Fit PPE headers
Fit race cats in H+S system
RR tune with hand commander.
I'm expecting it to be around £3.5k in total but may fit headers myself
Would like to supercharge next year but depends if the wife wants a conservatory.
To be honest, it's all about the noise for me, it's the sole reason i was in the market for a V8 in the 1st place
Marcus