Planning out your tank and researching over the next year is a good plan to start with.
Really a bio-wheel filter isn't going to be much good for anything other than running carbon. It's hard to octo-proof a hang on filter, and you're going to need a filter that's made for a tank 3 times the size of your tank. You're really going to want that sump and a quality skimmer. You probably won't find a Bimac anywhere around the DFW area. Dallas North Aquarium gets octos in occasionally, Rift To Reef in Lewisville had an octo not long ago. Some other stores might be willing to order you one, no telling what you might get though. Really I find it easier to order one online, although it is nice to be able to see it before you buy it so you don't end up with an old dying or otherwise unhealthy octopus. Cuttles probably are a tad bit easier considering they won't climb out of a tank, so no octo-proofing the tank is necessary, although they can injure themselves bumping into things if startled which can lead to infections, exposure of their cuttle bone, death.
I would recommend a tank with a larger footprint, so either the octopus will have more of a horizontal plane to crawl around, or the cuttle will have more room to swim without more risk of bumping into the sides of the tank. Also, just FYI, but that eel will not be compatible. Octopus is eels favorite food. Really to get the most out of a ceph it should be housed alone.
If you're not already a member, or at least aware, you should check out
www.dfwmas.org and that will help you close in on what's available in the dfw area. Several stores post their shipment inventory in the forums, and you can find good deals on used equipment from other members, like live rock for $2 or $3 per pound, or even complete tank setups for real cheap if you decide to go with a larger tank. Most of the members are friendly, helpful, honest, and experienced.