I've also got a fluval 405 and a sunsun 304 on my tank. While the fluval is by far a superior filter it's also over 4x as expensive. For the money the sunsun is a good filter though, it's built very solid and is absolutely silent though the gph could be higher. I bought my sunsun from KoolGoods, and I know many other people have bought from them too with good experiences.
Wow, my Fluval 404 is my piece of junk filter in my tank... but it is running next to an Eheim 2078 Pro 3 and a Magnum 350. From the reviews I had the impression the SunSun was much more filter than the Fluvals. I am getting close to giving up on canisters all together and going with my sump exclusively. Mainly because the canisters are so laborious to change that I don't clean them very often.
P.S. My Fluval 404 (Got it used with my tank) only leaks when I don't put it together properly... which is almost every time.
For $50 I don't see how you could beat the SunSun. I don't know of any Eheim you can buy new for only $50? I certainly don't think you will get a new XP3 any where that price range.