Here's all the options I can think of, in order of easy to hard (mostly)...
* Phillips WhiteVision H7 bulbs (or similar) - brighter and whiter than your old H7 bulbs. I tried these and they were, but not by much, don't expect much. Pros : drop in replacement. Cons: don't believe the ads.
* New/Used Litronics - Pros: the real thing (tm), easy - pop your old ones out and these in, maybe resell your old ones? Cons : expensive (used) or crazy expensive (new). Old tech. Still won't have the fancy auto level or washers if your car didn't have them originally.
* Single bulb xenon (as per you link) - replace just the low beam with a xenon bulb. Pros: proper xenon light, not too hard to install, should fit in old bulb holder ok. Cons: Only replaces your low beams, still looks like the old lights (but whiter/brighter), may start to burn your lenses, have to start chopping holes in the back of your lights for the cables to go through & mount the box somewhere on the outside of the housing. Also most importantly you won't have a projector so you'll be dazzling oncoming motorists with your unfocused death beams!
.... from here on in you're into baking and opening your headlights... if you're not up for that stop now! All these options are about the same level of difficulty, and ranked more on final results...
* Chinesium BiXenon HID kit from AliExpress etc - cheap tacky plastic mass produced kits from China. BiXenon replaces both your high and low beams in one unit, giving the 'new' lights look. Loads of options for projectors to give them various looks. Pros: cheap, loads of options for styling. Cons : cheap = can look tacky, have to open your lights, may have to get crafty with a dremel to make them fit in the lights properly... and most importantly you get what you pay for and these are generally pretty damn cheap... sure Nine8Six can chime in here on the dangers of your whole car going up in smoke when these fail.
* Morimoto Mini-H1 kit ... the same as above but better quality control basically. Bit more expensive but less likely to go bang. Will still have to do the same dremmel work to get them to fit as they are 'generic'. These are what the chinese manufacturers all copy.
* Nine8Six's headlights ... basically as above but better... you've probably already salivated over the 500 page thread and all the sexy pics... they are still a BiXenon HID kit but custom made for our cars so they fit perfectly and look classy, while using high quality electronics and metal shrouds that hopefully won't try to turn your car to ash when you turn your back. Cons : he's not currently making them, if you want them let him know and wait patiently like the rest of us for the next round... and hope he doesn't get sent to jail or almost die again before then ...
So that's it really, it all depends on what you're going for and how much work you want to put in. Opening your headlights to do a BiXenon HID install isn't for the faint hearted (they aint cheap these lights!) but it's also not that hard. And despite all the warnings about the cheap Chinese ones being rubbish, I've had a set in mine for about 6 months and I'm still here (touch wood)... although I also have another set of lights tucked in a box waiting for Nine8Six to get back to the lab and work more of his magic....