IMO, if you're planning to do serious astro-photography look at RAW (uncorrected) PE and capacity. Raw PE is indicative of the mechanical quality of the mount. Anything more than about +/- 5 arcsec and you're likely (though
not certainly) be in for some frustration with long exposure work at a significan't focal length (>1000mm). As a rule of thumb, make sure the capacity is about 25% MORE than your equipment weighs.
I have owned an Tak EM-400 - the images I got speak for themselves. Rarely did I throw away subs because of guiding issues even at 1760mm. The raw PE was a smooth (ie low frequency=easy to "guide out") +/- 3 arcsec and the capacity was 38 kg (conservatively). Total weight of my OTA and accessories was around 28kg
If your budget is your main constraint, ignore everything I said but spend as much as you can!
Cheers, Marcus