New / Bigger Kiln - first thoughts

I think I've maxed out my little 13" heptagon (7 sided) kiln.  It runs on 120 volts and is in perfect working order.  It is from Evenheat and has a great controller.  It just is limiting on the size / shape of work I want to do.  The seven sides, not sure why not 6 or 8, are a little weird.  I can get a 12" round kiln shelf in there.  Not too bad, but I'm limited to a square about 9" on a side.  That is OK for a small plate, but really not for the art I want to make.  

I'm thinking of a square-ish kiln that is 24" x 24" or even 24" x 36" and reasonably deep enough to do some castings that are melted through a flower pot.  That requires some depth for the mold, some space above the mold surface, and then the flower pot filled with glass.  That is probably in the 14"-16" depth.  That is a pretty big kiln.  

I've been pricing them out and they are from $1900 to almost $3000.  That is a high price for the convenience of being able to unpack it and just plug it in.  One the other building it myself gives significant cost savings, probably well under $1000.  But I need to find a way to work with the metal structure.  I don't have welding equipment.  Perhaps I can beg/borrow/rent some.  I haven't welded in 25 years, but should be able to re-learn enough as all I'm really building is a big box.  The controller is the highest cost item with is a couple hundred bucks for what I want.

I'm about to start pricing out the components - metal, firebrick, wire elements, controller, miscellaneous hardware, and other various and sundry items.  I'll document what I find and ask for help / opinions.