[Darryl Ramm]

Folks have already given you basic recommendations.

I would get 32 Gb RAM (16GB is minimum). 3rd party upgrade if possible. I'd want a 27" screen.

Get the largest internal SSD you can afford. Don't get a hybrid drive (as already mentioned). Ideally you can put audio/session on that boot drive. That is much better performance than any HDD, and most other SSD you can get. Unless you need huge disk space for samples, stick them on that boot drive as well. Ancient rules about dedicated audio drives do not apply to these super-fast NVMe internal SSDs, and your system will run *worse* with slow dedicated drives. Repatriate your current HDD for backup drives or bookends.

Ideally get a computer with an i7 or i9 CPU and fastest graphics you can afford.

Answers here are likely to end up in "max out the systems". It's not our money and we have *no* clue what your financial tradeoffs are. Your best crude guide for your to start at is your understanding how your current sessions are running on the hardware you have. That's a predictor of CPU needs, disk space needs, etc. memory well, no, you need lots more than with 10.

The Mac Mini is another option.

You'll need an Apple Thunderbolt 3 to Firewire adapter dongle, or a third party dock with Firewire, like the OWC Thunderbolt III dock.

And you may not need to be doing everything at once. What exact configuration MBP do you have now? Model/EMC #? CPU? Disk? Memory? You may have options of just upgrading that and running 2018.10 there today. If only to test stuff out. personally if there was any chance of staying on the MBP I'd do that and look out for a new Mac Pro next year (as others also mentioned here)... but that's my bias for a high end systems, may have no relevance to you.

Depending on what computer you should be careful about understanding what is upgradable easily, upgradable but a PITA, or not upgradeable at all. If the CPU, SSD and/or DRAM is soldered to the motherboard then it's impossible to upgrade, most things on the iMacs is at least a PITA to upgrade if its doable at all, the 27" iMac do have user accessible DRAM for easy upgrades, the 21.5" do not. I think the 27" iMacs have M.2 "like" SSDs cards but they are Apple proprietary and I don't know if third parties have upgrades yet, but even if they do it's a total PITA to open up the iMacs... so hold your nose and pay $$$ for as much SSD as you can now.