Try 15000-18000 you can pick up an R33 gts for less than 10000
Don't be so hell bent on a skyline they are not the be all and end all of cars yes they are great but it will be many many years before r34 gtrs are sub $30000 currently $50000-$70000 yes they look great but most 90's JDM cars look great,
also not bursting your bubble but you haven't even driven a skyline turbo/ twin turbo or NA so what makes you think it's gonna be any better than a Silvia or any other car?
I've owned 2x r32 gtst's, r33 gtst, s13 Silvia K's and s14 and driven an s15 and r34 and im very happy with my s14 and was also very happy with my last r32 I suggest you try as many cars as you can before you make a decision based on others opinions and looks