Thanks for the advice, everyone.
After checking some prices on the net, trundled off to the local computer dude to see what he had. The choices were (in Australian dollars, better known as Banana Republic Pesos): A Ti4200 with 128Mb at $240, a Ge4 64Mb DDRAM for $100 & a Ge4 64Mb SDRAM for $80. After some humming & hah-ing & discussions with the dude, decided that considering the computer it was going into (and the need to save up for a new system to run CM2), the best option price/performance wise was the DDRAM Ge4.
Tried installing the little bastard , but was getting a series of 3 beeps (1 long, 2 short) as soon as the power came on & black screen. Checked it was properly seated, swapped back to the old card (worked OK still), back to the new, same problem. Back to the shop I go. Dude tries the card in another machine, card works. Try the SDRAM Ge4 in mine & works OK. The best we can figure is that my poor old motherboard (K7M) can't supply enough juice to run the DDRAM. Cut my losses, take my $20 refund & head home with the SDRAM card.
Good news is, the card works very nicely & scrolling is much better, particularly on large maps, which were a real grind before.
As far as other options go, it's a Slot A motherboard, so I've got just about the quickest processor you can squeeze in. The extra RAM is probably the next (& last) thing I'll do, just to cut down the amount of disk activity going on (just enough to annoy me every now & then).
Thanks again for all the info.