Decent HID kits can be had for around £50 or so.

Decent set of bulbs are maybe £20-£30 but not as bright.

I fitted a set of HIDs to a friend's SEAT Leon and they were very bright 5000k but the beam scatter was horrendous, lit up houses like a police helicopter was locking onto them

90W would work although I never risked them for fear of frying my wiring at that wattage.