when you say youve already replaced the original bulbs with xenon upgrades, what did you actually fit?
this sounds like a common mistake made by many many folk i'm afraid!
xenon is another element, similar to halogen, within the inert gas table, only to get light from it, takes masses more input energy.
standard halogen gas emits light by being excited with just 12v input, true xenon gas on the other hand requires something like at least 20,000v and at different frequency to excite the molecules, and this is where the name HID comes from, High Intensity Discharge, and why HID kits require the ballast units to ramp up and control the voltage from your original 12v headlamp feed, to the 10's of thousands required to feed a true xenon lamp.
what you probably installed, was actually a halogen bulb, with blue tinted glass or coating, which although looking a pretty colour, serves no gain whatsoever, in fact many would argue that the blue tint actually reduces the light output because it filters and reduces the very colour spectrum of light we would like at night, in the interest of getting that true xenon gas light colour only!
so, if it doesnt have ballasts to hit the lamp with thousands of volts, it cannot be xenon gas, just a halogen lookalike, and very likely worse light output than a good new halogen, but a pretty colour which fools us,
there is an online store called hid's direct that i have used previously, and ebay is absoloutely littered with kits from as little as about 20-30 gbp, but the qualities do vary quite a bit,
the very first kit i fitted, more as an experiment to try a kit out, was the cheapest kit i could find on ebay, and is still going strong, 5years later, fault free, with only one blown lamp to date, so you dont neccessarily need to spend a fortune to get an effective and reliable kit,
in fact, some dearer kits i've used were different boxes, identical loom, connections, and equipment to the cheaper stuff, so dont overspend thinking it will be masses better in any way, but may have a longer warranty?
but you must have a good clean headlamp circuit to begin with, and, plenty of oomph in your battery, make sure these are all good first
cheers, good luck