Since 2004 I've been using record storage units similar to those in jimtranr's post #4.
I buy them from
Tony's Woodshop
I like wood in my audio room.
The units are all wood, modular, built with screws not glue and designed to stack and accept bases and tops. Bases and tops are 1, 2, or 3 wide. You can get them in oak or cherry (he no longer makes maple) . finished or unfinished. I finish them myself with a stain and polyurethane coating.
Here is a 6 unit with base and top. The components shown add up to ~$370 which is less than the Boltz 2 unit. It would be simple to add another row of three. I have a total of 28 in various combinations. Very sturdy, a single unit full of records is easy to pick up and move.