Mac Pro 1.1 to 5.1 comprehensive upgrade advice?

Question

I need some comprehensive advice on upgrade process, over the next 2-3 months, from my current Mac Pro 1.1 which is:
Dual-Core 2.66 GHz
8 GB of 1033 ram
120 GB OWC Mercury Electra 3G SSD (boot and data)
SSD backed up to internal 500 GB Hitachi Drive (CCC)
SSD backed up to external 250GB FW800 Drive (CCC)
Running Lion 10.7.5
2- 23” Cinema displays @ 1900x1200 res,
Nvidia GeForce
I’ve had this rig, give or take, for four+ years.
Main complaints:
Slow Excel and Word updating and editing, Some charts take 5-10 seconds to appear or redraw, in spite of font fixes, 0 ‘recents’ setting, keeping a very clean ‘permissions’ set-up, and other good ‘housekeeping’.
7300GT PCI card starting to get a little "quirky" with occasional mangled screens
Occasional ‘spinning ball’.
McDraft slow to redraw.
Generally, the 1.1 seems to be a bit too slow for me. I'm waiting on the computer, too much.
Would like somethingh that has a bit more ‘pop’. I like for the computer to wait on me, rather than the other way around.
Also, have not ruled out that I might be using some more ram and CPU-intensive apps in the future.
In looking at what’s out there used, and from what I read by the experienced folks here on the forum, I see the:
2010 or 2012 Mac Pro 5.1,
3.33GHz six-core,
w/ 3-8GB Ram,
1 TB Drive
5870 PCI
Moving up to ML or Mavericks.
as a very good ‘bang-for my-buck’ candidate. $2000+/-.
I intend upgrade the ram in the 5.1 to 24GB (3x8GB) @ $300., unless somebody talks me into higher, or another ram config.
Since my total usage for the last 3-4 years has remained fairly constant at 70-75GB, I intend to use:
My existing 120GB SSD as a boot for the new 5.1
Buy another 120GB SSD for a data drive
use the 1 TB drive with 2 partitions, to back up the Boot and Docs SSDs,
then do “belt and suspenders similar B/U with the existing Hitachi 500GB drive
all with Carbon Copy Cloner, and bootable.
Will be running one, possibly two, more 23” Cinema displays (or maybe a 23" and 27”)
User usage profile:
Lots (50-60+) of heavily cross-linked Excel workbooks (many with ten to twenty 2000-3000 line, work sheets) with tons of complex charts, in 15-20 folders.
A lot of long Word docs (100-150) pages, many of which subscribe to the Excel workbooks.
Medium to large, complex, symbol library-rich drawings, in MacDraft
Illustrator – light usage –simple stuff (amateur)
Photoshop – light usage – simple stuff (amateur)
Just getting into some GoPro Movie editing, nothing too big or complex. Vacation and recreation vids. (amateur)
Some Garage Band stuff for my harps (amateur)
Some 40-50 slide PowerPoint stuff, with more to come.
Dragon Dictate, which is a bit sluggish on my 1.1.
Questions:
Am I about on the right general track?
And I’m ready to get something I can live with for another 4-5 years. Realistic?
Ram upgrade to a minimum of 24GB -32GB? If so, Should I add 2x16 GB ram modules or 3x8 gig ram modules?
Will be leaving some, but not too much, processing speed unused?
What have I forgotten or gone astray with?
Better/cheaper upgrade?
Advice?
I know this is a long request, but I'm tying to make it in one concise and unfragmented attempt.

Answer 1

A couple(?) of clarifying questions:
Are you recommending upgrade to ML10.8? Isn't there some sort of hack involved with that? Or is it just the 32vs64 bit video issue. Anything else?
I believe he meant that buying the 5,1 would give you few benefits beyond being able to run any OS X beyond Lion.  And this might not be critically important for what you do.
You could hack it to run 10.8 or 9, I guess.
However, a new 5770 will take care of the 7300GT/0SX10.8 incompatibility issue, correct?
A 5770 will not allow you to run 10.8 if that's what you meant.  It will work in your Mac Pro so long as you are running, at the earliest, OS X 10.6.4.  That 7300GT is overdue for an upgrade.
50% head room on boot SSD? How do I find how much of current usage is boot? Subtract docs and apps folder sizes from total used?
If I understand...use a new Samsung 250GB SSD for boot and use my existing OWC120 SSD for docs and apps, and that gives me all the head room that I would need, for both SSDs?
SSD for the OS X system and apps only.  System is only 10GB or so.  How much space do need for apps?  50% of 120GB ssd is 60GB.  So as long as your apps don't occupy more than 45GB or so, then you can use the 120GB ssd as your boot drive.
If you don't feel the need to run the latest OS X, then more Ram, a 5770 upgrade kit, and an SSD boot drive should give you a nice boost in performance for just a few hundred dollars.