[G4] Upgrade dilemma(s)

[Slip Kid]

A common fork in the road?

My rig:

Power Mac G4 (Gigabit Ethernet)
1 CPU 400 MHz
L2 Cache1 MB
RAM 512 MB
Bus Speed 100 MHz
OSX (Tiger)
I only paid $177 for the above, then maxed the HD's and added a USB2.0 
so I have very few $'s in it.
Plus, it was 'only' supposed to be a 'way to learn' on a Mac as I have a 
2.8Ghz M$ machine.
But, I ended up with the G4 on the front line & it's fine...except for 
audio/video work (A pain for audio, useless for video).
I think my 1/2 Gig of RAM is OK, & to double that is cheap anyway...but 
the CPU/Audio/Video memory is the weak link, too often.
I can upgrade the processor ($200 - $300?) and audio/video...But I will 
have 'doubled' what I have 'in' the machine $'s wise. It's not 'new' & 
I'd hate to double my investment and not the good choices (bang/buck)
Am I better off with:
1. "Used parts"? A couple hundred bucks for a 'not powerful' new CPU 
seems steep, (a several year old Intel MOBO or an M$ box is 'cheap' by 
comparison)
2. An Intel 'Mini'? I can't afford it now...Is 'save and wait' a more 
realistic 'step'? (What or how may the Mini be 'less good' than my G4?)
3. Or, is there an el-cheapo 'boost' I'm ignoring. (The CPU spike is 
most obvious, so the 400Mhz is my biggest problem...but most costly 
solution)

Or, if I only spent $300, now...'where should the money go?'   'How 
dramatic' will a $300 'fix' (result) be?

thanks

Michael