Originally posted by mickazoid:
 And bear in mind I'm Classic Traveller only - I've never played any of the other Travellers, so I'm not up on the 'Grand Census' stuff...      
		 
		
	 
As William said, GC and GS are both CT books.  And, there's A LOT of great stuff in both of them that would compliment the work you're doing with these sector/subsector books.
Grand Survey brings a lot more "detail" to the world detail you're creating in your books:  Stuff like mean surface gravity, rotation period, detailed atmosphere composition (just what kind of taint is it?), hydrographic terraforming, temperatures based on latitude, various world mapping aids, number of cities (and population modifiers for those cities), how many ports the planet has (both space ports and star ports).
This data (and more contained in the book) are used for "creating" that planet.  You can place volcanoes and mountain ranges due to the info contained it.  Maps of the world will come with Surface Movement Rates for GMs to use in specific terrain.  Charts can be made for weather effects and temperature (which would greatly compliment your encounter charts you're already putting in the books).
Stuff like that.
Grand Census has more data that would be good for the type of book you're making:  Stuff like varying a world's TL based on different tech categories (a desert world probably won't have a high TL for watercraft);  Social Outlook of the various peoples on the planet (measures different aspects of the culture of the beings found on the world--very useful for roleplaying);  more detail is put into the planet's system of government;  indications of native intelligent life (maybe non-human);  religion is looked at..etc.
I think that both of these books, and the output they would bring to your project, would be a boon for your subsector books, taking them to the next level.
A GM could open one of these books of yours and have an entire worlds fully described, at his fingertips.
You might consider tracking them down.  But, be warned:  They're not cheap.  And, they're hard to find.
I have both GS and GC, and I have the MT version of both of these books (called the MegaTraveller World Builders Handbook).
I'm actually more partial to the GS/GC editions, although the MTWBHB is a fantastic book in its own right.
Many people will tell you that the MT version is just the re-printed stuff from GS/GC.  Although much of the MT book IS taken from GS/GC, I disagree that they're the same work.  There's definitely stuff that one has that the other doesn't.
If I had to choose, being a CT guy, I'd go with GS/GC over the MT book (but the MT book is 100% useable with a CT game--and provides much of the same "output").
You should consider getting them.  They're examples of some of the best stuff ever printed for Classic Traveller.