originally my system budget was under a $1k to get speakers and a receiver. its grown in the past couple of weeks for reasons i cant explain. so i have a klipsch klf-c7 center, forte main speakers and kef c40s or polk monitor series 4 for rears. i will also eventually get a svs pb10 for a sub. just bought a nakamichi pa-1 5-channel power amplifier and dont know which preamp would go good with it. obviously i could get a ca-1 but i cant find it anywhere for sale currently. i need some recommendations for the preamp for under $600, new or used.