I currently have a 150SSS on my 120 gal tank and love it. I have found that their skimmers are underrated size wise, thus they can handle more than listed. I will need to look at the footprint of the 300SSS to make sure it would fit in the sump. I just want to be able to keep the waste down as low as possible as I will also have SPS in the tank as well and I don't feel like having to clean the detritus from the sand bed every week, lol!!!Personally, I went for the Regal 300SSS instead of the 250SSS since the 250SSS and 300SSS are basically the same price. Considering your tangs I'd go for the 300SSS to be safe. Just my 2 cents. Totally up to you both will work great IMO.