[Rikakiah]

Doubling a budget can be hard to do. I personally would just drop the semi requirement and go with a reliable pump. People have given good options there already. I'd probably go with a mossberg 590 or rem 870 to start with.

Personally, I would prefer a bullpup as well, the KSG being at the top of the list. I'd heard many of the initial problems are gone with them, but there's still the price and availability. Incidentally, there's a conversion for the 870, but it looks ugly (built around the reliability of the 870, though). For me, I opted to just rely on my pistol until more affordable reliable bullpups became available.

As to kitting it out, do what you want with it, but keep it as light and maneuverable as possible. I would personally need a pistol grip as I can't stand/use a regular shotgun grip. A light may be handy (since you can't have 1 hand free for a flashlight). Instead of 2 sights, maybe look into some more basic night iron sights (tritium, etc). Save a little weight and still be practical. You're not gonna be speed clearing rooms, so you don't *need* a red dot. Keep it non-electronic and you won't need a backup, either. That's probably all I'd put on it.