Something close to Sash! and La Bouce would be stuff like Armin Van Buuren, Above & Beyond, John Askew, Gabriel and Dresden, etc. For Scooter/Prodigy I would go with Pete Tong, Hernan Cattaneo, Eric Pridz, Fergie, and others.
Your best bet- don't look for albums. Look for radio shows and live sets, and go from there.
Armin Van Buuren has a show called "A State of Trance"
Above & Beyond- "Trance Around the world"... that's a good start for trance
With house/progressive I'd go with Hernan Cattaneo's weekly radio show Live from "London", and Pete Tong's "Essential Mix" on BBC Radio 1 (most popular and most downloaded dance music radio show in history, which you can listen to bbc.co.uk)
Go to
www.tribalmixes.com, register, and look for the above sets, it's a legal site.
In particular, get AvB's A State of Trance episode 300- it's fresh and simply amazing.
What you get online is mostly one mp3 file 2 hours long. What I do is split these sets into individual songs and appropriately id-tag them. I can give them to you through MSN.