Don't replace that microcontroller with a DSP if digital filtering is part of the problem. QuickFilter's SavFIRe (Adding A FIR Filter After An ADC Gets Simpler, ED Online ID 13822) chip may be the answer. It handles finite impulse response (FIR) filtering in hardware. This is often a task tackled by a DSP or an FPGA. The $2.98 SavFIRe chip may not solve all your problems but it just might.
Trying to use the chip could take a bit of time if you develop a platform yourself and developing a complete kit was a bit more of a job than QuickFilter wanted to take on. The QuickFilter's SavFIRe Target Board for MSP-eZ430U (see the Figure) was the solution they came up with and it is rather elegant.
Texas Instruments' (TI) MSP430 is a good match to the SavFIRe. What QuickFilter did was to put together a board that plugs into the $20 MSP-eZ430U from TI. This puts the onus on TI for development hardware and tools while providing an inexpensive evaluation platform.
QuickFilter's board plugs into the MSP-eZ430U USB-based debugger. The board contains an MSP430 coupled with a SavFIRe chip. An analog input is connected to the ADC on the MSP430. The ADC data is shipped out of the microcontroller, through the filter chip and back.
The target board lacks the header found on the MSP-eZ430U's standard target board so you can't plug the QuickFilter board into another platform once it is programmed but it does provide an excellent evaluation platform for the FIR functionality.