The best options in order to find these 'high-end' games like CS or PG are the collectors network, newsgroups or via forum messages between collectors.
I agree with you but the main problem as you stated bruno is that
during the time you spend to acquire these data (or trying to acquire I would say), someone else will come and buy the cabinet 'with no question'.
That's true, and in my opinion as experience (on other games - LD games) this is the main problem dealing with other collectors
I don't know if the price is higher on ebay, though..
it depends on the game and the financial moment on Ebay imho
Now on ebay.com you can grab a Dk in USA for less than $1000 in mint condition
4 years ago it was a dream
And, at the end... ebay US may be an option,
Yes, for many people I think for clearness it would be the best one because people as stated before prefer to choose on its own
the cab
the condition
and the price
instead of a locked choice (example a defender cab - on ebay you find 5 a week at the conditions and prices you want - from one warehouse they have 1 or 2 at higher prices of course)
but you must have a local contact over there who'll manage all the things for you (shipping, etc...), or ...you'll have to pay the high price 
For that I can help but my warning is most on the fact that people are not used with it yet
and this makes me wonder..
MAv