Server: 4-8 core server with ~2-4GB of ram per core (depending on number and activity level of users) paired with either a RAID5 of 4 discs if you need lots of space, or RAID1 with 2SSDs if there are just a few files. Run SBS for 'ease of setup and use'. It will act as a file server, print server, remote access, and email client. Outsource your web server, it is cheap and most services run with nearly 0 down time, where as if your office has a power outage in the middle of the night you will never know until the next morning.
Then build a 2nd identical setup in preperation of a hardware failure. Set up a backup plan; Do disc/tape images every few months, and do an offsite backup (VPN to somewhere, or a cloud service) for the rest of your files which should be done nightly, but you do not want it in the building with you in the event of a fire.
Office PCs should get i3 cpus with 4GB of ram, production machines should get i7s with 8-16GB of ram (possibly more depending on file sizes... last time I used autocad was r4 lol), and possibly a quadro or firepro GPU depending on just how intence of projects we are talking here. All PCs should get a ~120GB SSD for programs, all files should live on the file server. Just about anything can run duel monitors today, even little i3 CPUs, just be sure to get ips displays for your units.
Not too sure on tablets yet, but win8 tablet are coming soon, and if you want something useful I would wait for them. Otherwise I would likely pick an android for the moment... but having never used an android tablet I really don't know what to tell you there.
Consider one of these down the line as the tech gets cheaper:
http://www.microsoft.com/en-us/pixelsense/default.aspx
There is potential for this to be an amazing presentation tool, but it really isnt ready for prime time yet.
Well... that wasn't very specific, but neither was your original post. Servers can vary in price from hundreds, to hundreds of thousands of dollars. Office machines can range in price from $400-2,000, and production machines can range in price from $1,000-30,000 depending on exactly what you require of them. So without some form of at least ball-park budget in mind it would be impossible to go further.
This really needs to be handled by a paid professional who knows your exact situation, your building, your user base, budget, clientel, and can provide some sort of support if the whole system goes to hell. You say that the sky is the limit on budget, so spend good money on someone who knows what they are talking about; it will save you thousands in hardware and software mistakes.