You're preamp has plenty of gain for just about anything, though you may need to crank it up more on the real flea outputs. But it only goes to 52 Ohms for MC? Should that be 520 Ohms? 52 Ohms will sound dull with some MC carts that like over 100 Ohms (e.g. Benz low output carts).
I have a Gyro SE with an SME 309, so very similar to your rig. Cartridges I've used with it:
AT150MLX (MM)
AT33PTG (.5mV)
Benz Ace High (2.5mV)
Benz Wood L2 (.4mV)
The latest incarnation of the Ace is at the top of your price range. It's good all around, except for only OK tracking, but what it's really got going for it is its lively "you are there" midrange. The L2 is even more startling in this regard and more refined all around (though no better at tracking), but I think I could live happily with the Ace. I haven't heard the Glider, which is in between these in the Benz lineup, but I prefer a body on the cart to provide at least a little protection to the cantilever.
The AT33 is smooth, neutral, with a sweet treble, excellent dynamics, and is very quiet in the groove. It tracking is excellent. In some ways, certainly in quietness and tracking, it bests even the L2, but lacks the midrange transparency of the Benz carts. Dropping the loading as low as possible (AT specifies 20 Ohms and up) may help in this regard. This is the cart I'm currently using. I'd have stuck with the L2 but for the retipping expense.
The AT150 has a very clear, realistic midrange and good bass and "PRAT", but I found the top end rather wearying. This may be a case of getting just the right capacitive loading. Like the AT33, it's an excellent tracker.
