I received three gently-used CPU/MOBO combos from a like-minded friend which I decided to use to stave off a new home-computer purchase for myself, and with them began a household upgrade path which turned out to be far more intensive than I was anticipating.
While it sounds easy enough to 'flowdown' better boxes to replace the older ones, given the disparate heterogeneous environment I run at the house, and why, it was rather hair-raising for a week or so while I took inventory:
MEMORY:
1 x 1GB PC5300 DDR2
1 x 1GB PC3200 DDR
2 x 512MB PC4200 DDR2
1 x 256MB PC3200 DDR
2 x 1GB kit (dual-channel 512MB PC3200 DDR, 4-sticks total)
1 x 128MB PC2700 DDR
2 x 256MB PC2100 DDR
3 x 512MB PC-133
4 x 256MB PC-133
1 x 128MB PC-133
1 x 128MB PC-100
3 x 64MB PC-100
3 x 32MB PC-100
STORAGE:
1 x 36GB 10k SATA Raptor
1 x 80GB IDE
1 x 120GB IDE
1 x 160GB SATA
3 x 160GB IDE
1 x 500GB IDE
1 x 500GB IDE external
2 x 30GB IDE
2 x 40GB IDE
CPU:
1 x 3.60 P4 (HT?)
1 x 3.06 P4 (HT?)
1 x 2.80 P4 HT
1 x 1.60 P4
1 x 1.42 PPC
1 x 1.25 PPC
1 x 866 PIII
2 x 500 PPC (dual)

The first thing I did was was upgrade little girl from a non-functioning 1.1GHz Althalon box to the 866MHz PIII and put in 896MB of RAM. XP runs remarkably well in this configuration considering the only thing she does is play her online flash games. She has to run XP because there are no linux drivers for the WPN111 USB networking client I needed during my 6-month stint in a STL hotel, and everything but the office has to connect wirelessly.
I'll likely upgrade the boy to 512MB of RAM, splitting the PC4200 pair as the mac mini contains only a single slot. Its not as much as the 1GB I run in mine, but it will double what he's currently running.
Those are the easy ones. I really don't know how I'm going to lay out the rest.
I'd like to take darkvoyager, my current ubuntu server and yank out the 500GB drive, leaving its 30GB root drive, but populating it with all the leftover single sticks of mixed speed memory, letting it run fully populated lowest-common denominator, and installing XFCE on it as my wife's new desktop. Its a 1.6GHz P4 and I should be able to put in the remaining 512MB PC4200 stick, the 256MB PC3200, and the two 256MB PC2100's for 1280MB (right now it has one of the dual-channel PC3200 kits in it). She only uses the browser, but demands a snappy response, which the RAM upgrade + XFCE should accommodate. I don't know what I'll do with the PowerMac G4 (dual-500MHz; 1.75GB RAM) it will replace. I've considered putting ubuntu on it for giggles because there's nothing else I can do with that box right now.
My mac mini will go atop the rack, and I'll only use it for VNC, likely moving my iTunes database onto a linux vault of my creation. If I put both sets of dual-channel 1GB kits in my current XP box and pull out its amazing 36GB Raptor. I can use it as-is, and simply add my two 500GB drives to it, and let it boot off a 30/40GB IDE, leaving the 160GB IDE drive in it. Its a massive Antec case, so it has the room to be a great vault (its the one on the far right).
Let's talk about workstations. I think I'll purchase 8GB of dual-channel PC5300 and split them between the 3.60GHz and 3.06GHz boxes, loading the faster of the two boxes down with the SATA drives and putting the 80GB IDE drive in the other. Here's where it gets sticky: What do I put on what, and why?
I've been at this a week so far. Do I run XP on the faster box, or linux? Do I run XP in a linux VM or simply across a KVM? What are the benefits and shortcomings of each? Will the one box that will accept 8GB of RAM be seen by a 32-bit processor and would linux be able to see it? I don't know! So many possibilities. Let me know your thoughts?
Either way, this gift of processing power will probably give me another two years of life before I have to do all this again. Thank you. New hardware always makes me giddy!