This is the world's best Q45 site. And it's 3 in the morning, so all the members of the world's best Q45 site are sleeping in their beds. You have to give people more than 1 hour in the middle of the night to respond. People can't respond in their sleep.
Also, you will probably find a lot of info by searching. Not that we're not happy to answer your question, but being the world's best Q45 site, the topic has been covered before so a lot of answers are already out there waiting to be read.
In answer to the question, though:There's not really a single website solution for parts for ANY car. That's sort of a backward approach. Best idea is to determine what parts you want, then look for them. Google is a great tool. But there's not really a single Q45 parts site that'll serve all your needs.
Also you have to keep in mind that the Q45 has never had very good aftermarket support. There just aren't that many parts out there in the first place. And many parts are no longer made, but can still be found, in which case your dreaded ebay is indeed the solution.
For power, a good place to start is a NICO ECU, assuming your car is in good running condition (if not, rehabilitation is the best first step).
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For HID, I have no personal experience, but if you search the forums you'll find a lot of great advice, most of which is not model-dependent, so don't restrict your searches to just the Q45 forum on that topic.