It annoys me that your looking for a cheap good turbo... There is no such thing..! If you want a good thing (anything generally) you need to pay for it! Any turbo new is going to be expensive. Pay a good £250 for a decent K03s, but this alone will not provide you with the power you are in search of. You will need to spend AT LEAST £400 to remap it not including the other mods required.
If you are you looking for power, live with what you have for a while, save up and spend it all on a hybrid and all the other supporting mods and get her remapped to cope.