I've never bought from Metals Depot so i don't have an opinion. Looks like they're marketing mostly to tool-and-die makers, industrial stuff, and there's nothing wrong with that. Their prices for A2 and D2 seem to be a bit on the high side. One thing to consider though, both alloys are listed as precision-ground, which is a very good thing. That will save you time and belts... mill scale is very hard on belts and takes a while to grind off. Precision-ground stock comes very flat, straight and clean.
Keep googling and compare prices, there are MANY sources for good knife steel, including Admiral, Knifekits.com and Texas Knifemaker Supply, all of which sell a lot of steel directly to knifemakers. USAknifemaker is a great supplier, I always check there first. Tracy (BossDog) is the owner, and he does NOT goof around when it comes to keeping his retail site updated and shipping orders quickly. 2thumbs
No matter who you buy from, you generally get a better price when buying a 3' bar, and have more options to cut several knives out of one bar with minimal waste. Wider sheets are even a better deal per square inch, but you have to be able to resaw to the dimensions you want.
You've already decided to send your blade(s) out for HT... check out Peters Heat Treating forum here on Knifedogs or google their main website and ask for a quote. They're very well-respected and have good prices, especially if you have them do several blades of the same steel at once.
Looking to make a tactical knife, personally I would go with either D2 or 154CM. They're very similar in toughness (both pretty darn good) but 154 is more wear-resistant (keeps its edge longer, but is a little more difficult to sharpen... not ridiculous, though). 154CM is significantly more resistant to corrosion (although D2 is also pretty decent that way, it's "almost stainless" with 11% or so chromium) and takes a much better polish.
Honestly, from what you've said, I'd say get either D2 or 154CM in the size closest to what you want, for the best price. They're both dang good steels for knives that can work hard and don't need a lot of maintenance.
There are options for graying and even blackening these types of steels, but I have no experience with that.