I guess it comes down to what your starting with... My old 25 had tomei cams and tomei pistons when I bought the car running a TD06 made 300rwkw @17psi. I changed the turbo to twin t3/t4s, added 2 x 044 pumps, 1000cc injectors and made 399rwkw
Im pretty sure you could build 400rwkw for under 20k but my 26/30 ate up way more than that. lol