where am i located? i dont get it, like in my room?
also, ive been considering getting an a2-300 from all the amazing reviews of it but im confused about their website stating it only has 40-160Hz which is really bad cause the all the others are below 25hz right?


No, what state are you in? I have some gear I no longer use and if you are in the area, I can probably set you up.
I'm not familiar with that particular sub, but if it is an anechoic measurement, you will actually get better than that due to room effects.
If you are into hip-hop and other music with lots of low frequency energy, you would not be happy with that sub. But for standard music (classical, rock, jazz, country, etc.) 30-35 Hz is a pretty reasonable low end. In classical, for example, some of the lowest pedal tones from a big organ will be weak. You will still "hear" them because you mind takes the overtones and fills in the root, But your gut won't feel them!
If it were for HT and you really want your body/stomach to feel the impact of an explosion, that is where you want the 16-20 Hz subs!
At your budget, you don't want to chase after low frequency extension as you are liable to get a very un-musical sub.
You might want to read this review as it gives a lot of info on the trade offs in sub design in the context of a musical sub similar to what I believe is a good fit for you. Often this Emotiva sub is discounted to $400. My biggest caveat for recommending it, is that it may be under sized. Usually buying one and adding another later if you need more bass is an option, but Emotiva is pretty quick to redesign products. IOW, a year from now when you are ready to buy a matching sub, Emotiva may have replaced this model with an entirely different model.
Emotiva X-Ref 10 Subwoofer Review — Reviews and News from Audioholics
HSU is a good option. Call and talk with them about it. That will give you a warm feeling about who you are buying from - they are great about helping you determine what to get rather than just trying to maximize their profit off of you (I hope they have not changed - it has been 3-4 years since I spoke with them).
You really need your room dimensions to do this!