You really want to try them as some you will like and some you will not. As others have said there are many others that fit your price range such as the Celestron Ultima 65, the Nikon Prostaff 5, Viking AW 65, Viking AW 80, Hawk NatureTrek 60 &80, plus, as you say, Acuter and Helios.
A trip to a specialist will see you testing a number of these. If you live in, or around the county of Norfolk I would recommend 'Cley Spy'. They have a massive range of optics that you can compare side-by-side.
As others have said, you don't need 80mm and 100mm objective lenses. However you generally leave the scope on the line for much of the day so it really doesn't matter that much how heavy it is. You will not need more light than a 60mm will pull in though.
I have lost count how many scopes I have looked through, both on the shooting line and for birding. I have not found a sub ?120 scope that I would spend any money on. The use at 100 yds is questionable in competition, they are generally not waterproof and fogging of the optics reduces them to scrap in a year or three
The Acuter is interesting as it uses 1.25" eyepieces. The 1.25" fitting is a standard astro eyepiece therefore most astro eyepieces should work. Although asstro eyepieces are not waterproof neither are most of the cheap zoom eyepieces supplied with waterproof scopes. You will often see the scope listed as 'waterproof body' or being a bit vague about the eyepiece.
What is also interesting is that much of the optical quality lies within the eyepiece. Zoom eyepieces are always the weak link in optics and always out performed by fixed eyepieces. The Acuter should work with an astro eyepiece. I will try it with an Explorer 12mm ED eyepiece and report back. Note the Explorer 12mm ED is an outstanding ED glass eyepiece and only cost ?50.
I will be trying out the Celestron Ultima 65 and the Acuter 65 against my Pentax 65ED today and will report back, if it's in stock.