Hi, we are a family of four and have recently bought a 900 xp (the only difference is that the 900 has an extra bedroom - I think!!!) - we have used it once and thought it was wonderful! The weekend we used it was extremely wet, but it didn't leak and hasn't put us off camping at all - can't wait to use it again! Good luck in whatever you choose!!
The Vango Diablo (and Colorado) dome tents are very nice but what put me off was their massive footprint size. Dome tents just aren't a very good use of space I don't think - tunnel tents are the way forward.
Others will disagree of course - it's just my opinion :-)
------------- 01/06 - 06/06: Alston Farm, Salcombe
20/07 - 22/07: Wyke Down, Andover
13/08 - 18/08: Bracelands, Forest of Dean
Outwell Nevada M
Coleman Columbus 8
Vango Venture 500
Quechua 3 second
Think I agree on the footprint, we have just bought the 900XP and its footprint is 29.2 msquare, thats a big difference from our old Coleman Weathermaster, but as our family has also increased we do need the extra space, we have outgrown our weathermaster.