Doing both cpu and gpu on one comp is not a good idea. mining on gpu already uses alotta cpu with the gui client. they said the poclbm is faster if you dont usethe gui with it, but i tried it and i couldnt tell the difference in speed. it was still the same for me. i ran 6990 on both.
only solo mine if your either lucky, or have a great machine, maybe 4gbhash/sec, if not it might be easier to pool cus u see the income racking in every day. solo might take a week with a good machine, might take months to years with a bad one.
in the end, it is said that pooled and solo reap the same amount, but if ur inpatient, then pool. if u are patient then solo i suppose.