At this point it's a physics and money issue. How many panels can you physically fit VS how many panels you can afford. Looking around for used panels on Craigslist and the like the average is somewhere in the 250w/$100 range for old grid tie panels off someone's roof. That's the cheapest option if you've got the space to put them. On the other hand if you need to maximize space you're going to be looking at higher density panels which are in the $1/watt range, or say about $400 for a 400w panel. Same size as the used panel (give or take) but almost twice the power, and 4x the cost.
Brand isn't nearly as important as any brand of panel will perform about as well as any other brand at the same wattage rating. The big keys are that the panels be pretty close to each other in VoC and Vmp so you're not nerfing panels, and that your SCC can handle a decent number of them. The used panels for example usually sit around 40v VoC and if you wanted to do strings of them the SCC has to be able to handle it.
For example, you get some used 250w panels from a guy and they have a VoC rating of 40v. If you buy a SCC that can only handle 100v then you can only put 2 in series (80v) but 3 in series would fry the SCC (120v). Fortunately that EG4 3k you're looking at IIRC can take up to 500v so you could make strings 11 deep if you really wanted to, you've got lots of options.
what would be the best option on panels as far as brand/watt
OK, sorry, I rambled there a bit. Find that Venn Diagram overlap of what you can afford and what you want to spend and get whatever panels fit best in there. Being a cabin you've probably got space for the older used panels, Trina 250w are pretty common, and get a stack of those.
just going to use the 200 amp box since its already there
You'll want to throw a jumper between the legs in the box so you can feed both sets of breakers but that's easy enough and pretty common.
