Anyway, first, I dont know if your bp6 can handle a 1Ghz CPU, and even if it does, save some money and buy a 866-933 Mhz.
Secondly, more than 256 Mb is overkill.. PC150 is no good unless you're into overclocking, and a p3-1000 is not exactly a great overclocker (nor is the 933 btw).
(btw, you have a SMP board.. why not take advantage of it by buying 2 cheaper CPU's ? Only if you intend to run W2K of course.)
Lastly, if you're into games, spend all the money i just saved you in a good videocard, like Geforce Pro, or Radeon DDR.
I'm thinking you don't really need to upgrade either system. If you've already got the k6-3+ then why not, but other than that you don't actually need more performance for business apps. In many gaming situations you're not going to see an absolutely massive increase when going to 1ghz. The video card matters much more. You've got a nice video card so I wouldn't recommend ditching it quite yet. I don't know what the max speed your bp6 will accept, but I suggest finding out that speed and getting that processor.