Go with a proven DIY design. Don't attempt to design your own crossover until you get some experience - home audio is a completely different beast than car audio and crossovers will, most of the time, need to do a lot more than just sperate frequencies. The tri trix is one of, if not the, best projects for first time DIYers and parts express has a knockdown kit that will speed up construction. I built the tritrix and you cannot touch this thing with any commercial design for up to 5x the price. As far as the sub is concerned this you can do more of a custom design. The goal for a ht sub is to play as flat and as low as possible, unlike car audio where peaks are desired. This generally means you want a low fs driver tuned close to the fs in a large enclosure. A bash plate amp is a great starting point.
Bought from - Hazardous0388 (4 db Drive 2000.1s), Psychoacoustics (4 Powerbass XA 3000'ds), and blackedoutavy (PPI A200)
Sold to - D-Rew (Knu 1/0), d77543020 (Knu 1/0), F1McLarenAGR (Audioque 4x90), and SacTownBully84 (Knu 1/0)
Traded with - SacTownBully84 (my xa3kd for his xa1.5kd + cash)