Sean,
Since you are having the A90 fixed, it still probably pays to have an alternative that sounds slightly different--just to keep things interesting. The Titan is a slightly cooler sounding cartridge than the Orpheus. I cannot say how it compares to the A90 because I haven't heard a side-by-side comparison.
Any of a number of Lyra cartridges will probably be good alternatives (slightly different, but not extremely different). I have owned a number of Lyra cartridges and all have proven to be very long-lived, great at tracking, and quiet (low amount of ticks and pops).
Since you are having the A90 fixed, it still probably pays to have an alternative that sounds slightly different--just to keep things interesting. The Titan is a slightly cooler sounding cartridge than the Orpheus. I cannot say how it compares to the A90 because I haven't heard a side-by-side comparison.
Any of a number of Lyra cartridges will probably be good alternatives (slightly different, but not extremely different). I have owned a number of Lyra cartridges and all have proven to be very long-lived, great at tracking, and quiet (low amount of ticks and pops).