Welcome to GTT.
This is one of those loaded questions, ask 10 people, get 10 different answers and recommendations.
I have to ask on your mechanical abilities?? Seeing as you have limited the budget to under $1K, you will be in the market for something older that most likley will require repair upfront or inthe future.
I can't help on the green stuff, don't know about them and usually too much $$$ for me.
As for other brands, the simplicity/allis lines are good tractors, but stay with the 60's -70's stuff. I have a '70 Allis HB212, it was the best cutting tractor I ever used, currently waiting a motor transplant after 20 yrs of hibernation. Implements can be hard to find and sometimes expensive. The newer Legacy I believe is heavy built tractor, but doubt you will find one under $2000 with implements.
I have a collection of Older sears, Good tractors but they have their issues too. They use a "sub Cat 0" rear 3pt hitch meaning their implements have closer attachment points than standard Cat 0. Not to be scared though, they are plentiful if you look. Sears also switched to a SSI module ignition in '68 up through late 70's on their Tecumseh engines. They burn out and are very epxensive to find an exact replacement, but there are updated conversions for around $150. Sears also used the twin onan's in their SS machines which are powerhouses, but parts can be expensive. Sears did have a 3 speed tranny with high/low, very nice feature.
You mentioned the Craftsman. I shy away from the newer ones for anything other than mowing, but I know there are members I've seen add a rear hitch and work the ground hard, even a few with some types of front buckets. I think that 4000 you mentioned is a decent newer garden tractor.
Bolens and Wheel horse are also both decent brands
Of course Cub cadet will be close to the top too. Had I not gotten into the Sears, I would've went the Cub route.
One thing about implements, if you go with a sleeve hitch on your tractor, basically any brand of implement with a sleeve style hitch will fit that tractor. That will open you door some if you are looking for attachments.
Look through our tractor brands section and browse some. Maybe that will give you a decent idea of something that would catch your eye.