You'll probably spend less for the 14" off-brand one. The 18" is going to be going up before auction's end.
Ply makeup on Ludwigs is not set in stone. I've seen mahogany interiors that were painted, and maple interiors. I heard they used maple/poplar/mahogany, and often it would be either inside, but usually maple. On the maple veneer 3 ply drums they may be mahogany inside. They weren't all maple. The thing is, you need to have several Ludwig drum sets and look at them to be able to see the truth.
I think you could sell them and buy a Mapex Pro M set or something and then go down the road, UNLESS:
You think you may someday realize how cool the drums you have are. If that happens you'll have seller's remorse. The easiest thing to do is to embrace the Gold drums, purchase the bass hoops from mcjnic, and get some heads that make those drums sound the way you want them to for your music.
Extra floor toms may show up, those both don't look that great, spare gold sparkle Ludwig drums do show up on eBay sometimes, if you're patient maybe you'll be able to buy one that matches the set.
What did you expect to hear from us, anyway? The cool thing about vintage drums is they're such a great value. The set probably has a thin tom mount holder, so like Jonni said find a snare stand and put them to the left of the bass, and you have a cool offset tom setup.
Another option is to put out feelers for someone (perhaps a local drum collector in your area) who would like to trade with you. I have a 70s Pearl Fiberglass double bass set that has some fading on the wrap, but this is a monster set, and you could find a similar set locally, that someone would like to trade you for. Tama, Pearl, 70s or 80s era sets are in abundance and if you're careful you could get some nice quality drums in a more conducive color to your head-banging music style (I just interjected that assumption, if I'm wrong, my bad).
You're right to seek expert advice, though. It would certainly be a good idea to check with experts before trading, or before buying a used replacement set.