Wemfan,
I too have a McIntosh MC452 and had a McIntosh C50 (solid state) preamp, which I replaced with a C2500 (tube) unit, sounded a little sweeter than the C50...but then swapped out the stock tubes for a set of Genalex Gold Lions, once broken in, just sound so "musical". The C2500 is a "keeper". As this has recently been replaced with a C2600, you might pick up a good deal on one of the remaining C2500's.
I too have a McIntosh MC452 and had a McIntosh C50 (solid state) preamp, which I replaced with a C2500 (tube) unit, sounded a little sweeter than the C50...but then swapped out the stock tubes for a set of Genalex Gold Lions, once broken in, just sound so "musical". The C2500 is a "keeper". As this has recently been replaced with a C2600, you might pick up a good deal on one of the remaining C2500's.