After I built my new system a couple weeks ago, I discovered that I've grown a taste for it, so I want to do something with my old system. I have a bunch of parts sitting around unused, and the only new things I would need are a case and mobo (which would cost me less than $100). The current specs are:

Intel SE-440BX-3
Intel Tualatin Celeron 1400MHz
512 PC100 RAM
IBM Deskstar 22GXP 13.6GB ATA66
Western Digital WD400BB 40GB ATA100
ATI Radeon 9100 64mb
Netgear FA311 Fast Ethernet Adapter
Creative SoundBlaster Live! Value
Hitachi DVD-ROM
Mitsumi 4x4x24 CD-RW

What I would like to do is change this system, and my spare parts, into 2 systems. The specs would be:

MSI 694T Pro VIA Apollo Pro133T OR Soyo SY-TISU Intel i815EP
Intel Tualatin Celeron 1400MHz
256mb PC133 OR 384mb PC100 RAM
Western Digital WD400BB 40GB ATA100
ATI Radeon 9100 64mb
Linksys100TX 10/100 Network
Onboard Sound
Mitsumi 4x4x24 CD-RW

and...

Intel SE-440BX-3
Intel Pentium III 550MHz
128 PC100 RAM
IBM Deskstar 22GXP 13.6GB ATA66
Creative TNT2 32mb
Netgear FA311 Fast Ethernet Adapter
Creative SoundBlaster Live! Value
Hitachi DVD-ROM
Quadrant Cinemaster DVD Decoder

Now, the 1400 system would still be used for gaming, so would I notice much of an increase in performance with the new mobo? And also, which of the mobos and RAM combos would you recommend? The 550 system will probably be dual-booted with 98SE and Linux (so I can get a little more familiar) and used for the occasional DVD viewing. After all that, is this a worthwhile "project" or am I just extremely bored? I appreciate any and all opinions.

Edit: I also plan to overclock the 1400 system, and the SOYO motherboard is very overclockable. Is the celeron unlockable?

Nothing Intel makes is unlockable; except for their earlier PIIs I think.

In that case, I doubt I'll be able to get up to 133 FSB with it. Would I be better off synchronizing the memory at whatever I can o/c the FSB to or clock the memory at 133 and o/c the fsb as high as I can (likely less than 120)?