I've owned both you mentioned and it's a toss up between them. Pulsar has a slightly better image and better controls while the Zeus has a much more robust housing and a better mount. Also the Zeus is more compact and better ergonomics. Pulsar is somewhat ackward. Of those two I think I prefer the Zeus by a slight margin. That said if I were you I would look into a used 640 res unit maybe just slightly more than 4K. Once you look through 640 you won't be interested in a lesser resolution. I currently run a Zeus pro 50mm 640 and it's the cats meow but you could get into a used Zeus standard or a Thor (non HD line) for around your max budget. Stay away from the new Thor HD models from what I hear.