With the help of the SdFat library and by changing "Serial.write(dumpByte(currBank, currByte));" to "myFile.write(dumpByte(currBank, currByte));" it was very easy to dump the rom to an SD card instead of sending it over serial to a PC.
It takes 12.5 minutes for a 1MB LoROM/SlowROM game compared to 18 minutes over serial.
And 100 minutes for a 8MB ExHiROM/FastROM.
You just got to love the arduino 