I agree with gotfish that a 15 would alot better than a 10, but when I setup a new system and have to use the space in the stand for my sump/refugium, I want to use all of that space available. I stuff the biggest container into the space I can get.
Do some looking around. Many fish stores have used equipment laying around. Many hobbiest have stuff laying around. If your a diy guy, consider making one your self, out of glass or acrylic.
With sumps, bigger is always better.
I would use at the very minimum a 20 long. When picking a sump you not only want water volume, but you want space. With more room, you will be able to make a proper refugium, give you more options on return pumps and give you room for a proper skimmer.
That skimmer looks like a pos.
Do it right the first time and you won't need to fix it a few months down the road.