To start with, what's your plan for the car? A little fun on the roads?
Those seem pretty expensive to be fair, are you wanting a little more than stock is20 power? Or perhaps IS38 levels of power?
If what you have is a GTI, then an IS38 is a direct bolt on.
Have a look through the Littco page at options, had great reliability and power from the L380x and seen good things from the L500 too (albeit a little more lag on spool but capable of a lot more power)
https://littleturbocompany.co.uk/shop/p/snake-656as the L380x for reference which I have made 430hp+ on.