If you've got between 15-20K, you wont be buying a VY Clubby, let alone bring it up even 1hp higher man....
Not tryna be an ass, but i doubt you'll even find a VY Clubby for 20 or less, let alone modding it...
I got my VYII SS Ute for 15 (was ridiculously cheap, doubt you'll find any that cheap... mine has a small dent over wheel arch and a few little marks here and there, thats why i got it cheap, on top of doing a good job bumping down the car dealers
)
But you should find a decent VY SS under 20... i'd go something like that, then you got a little bit of money to play around with? Maybe some rims to make it look nice, then i dunno, an exhaust, extractors, then you'll be at 20...
But if you really want the look, go the clubby, then you still got quite a bit of power and a great looking car.... Really is your personal preference whether you want power/looks etc