you can record on your setup, hardware specs are not really all that important. You do not use a "sound card" to record things. Are you trying to record them all at once or each separate? If all at once i recommend
fast track ultra I have used this with great success recording. with these you can monitor your audio inputs directly with the headphone or monitor outputs of the unit. if they will be recorded separate you can look at the interfaces that have 1 or 2 inputs. I recommend the fast track pro model. Maudio also makes pci cards, but these generally do not include microphone pre-amps and are not as highly regarded as their usb/firewire offerings. other options are available as well, look for products from emu, lexicon, digidesign, and others.
what software are you going to use?
logic is mac only and on a similar level as pro-tools for recording but it has much better midi components
ProTools is an industry standard for recording. (the LE or "lite" version is more than you will probably need)
Audicity is free and works well for more basic stuff.
There may be more out there, do some research.
what kind of microphones for the vocals and acoustic? condenser or dynamic?
vocals: usually a dynamic mic is your best bet. a shure sm58 is the standard.
Acoustic: if you don't have pickups and a DI box, I recommend a sm57, again a standard.
look to the shure pg line for good mics that are a bit cheaper.
Base: Are you planning on recording the output of the amp or a direct in from the base? Most recordings use a microphone in front of the amp to get the distortion, and then mix in a direct line from the instrument also.
How much experience do you have recording? do you know how to do things like set your input gains correctly?
Even if you buy a mac mini you will still need to purchase an audio interface like the one above.
technically you can record with your creative card by using the line in, but you will not have a good way to monitor the input live, or set the gain structure. you will not have a mic preamp to boost the signal to line level, you will only be able to record one thing at a time and the quality of the recording will suffer.