Even though I no longer have any shrimp, or tanks minds you, I'd stick with the substrate you have left over, as you know it works well, stick to what you know I guess, plus you'll save coin also, filter wise, I'd go canister or air sponge, I've never used sponge though but have seen many, many successful shrimp tanks with sponge filters, I guess if you want the quiet approach go with the canister, if you don't mind a little noise go with the sponge, up to you, tank wise, stick with the same size perhaps, doesn't take up too much room, plus you can get a sweet colony going of shrimp, shrimp wise, stick to what you know, unless you want to explore over shrimp, nothing wrong with CRS at all, cool shrimp, great colour and once you have a nice colony going they will be easy to sell off, either culls or for the purpose to put the coin back into the tank and shrimp, plant wise, go with what you want, you already know how to successful grow HC (jealous), so why not test another plant, perhaps another carpeting plant, or perhaps stems, , as you know shrimp love mosses, could do a variety of moss tank, or do a complete carpet only tank, perhaps go down a variety of java fern tank. Personally I would go with another full HC carpet, you already have easy access to the plant, you've proven you can successfully grow it in the conditions you have, but instead of adding stone and stems in the tank, add a piece of gold vine driftwood, something that the shrimp can crawl all over and explore, when the wood leaches tannins the canister filter will fix that when fitted with Bio Chem Zorb, when the wood grows a fungus as it does at times, the shrimp will love feeding on it, but that's me. You could grab say 10 CRS off a member on here, 3 males, 7 females, a nice starting group and if all is well will breed in no time.