Your receiver may have a tunable RF amp. before the mixer. If so, its main function is to define the noise level and reduce 2nd. channel interference - not that that will be a problem to you since you are using an 11 MHz IF. Either way, the insertion of a "pre-amp" prior to the mixer is
not the way to solve your low-gain problem. In fact, if the receiver
does have a tuned RF stage - and assuming that it has a reasonable tuned gain - something like 10 to 15 times voltage gain - fitting a pre-amp. in front of it will seriously degrade the performance of the receiver - mainly due to cross modulation & similar unwanted effects.
The cause of your low gain is because you are using such a high IF.
11 MHz is
far too high for a receiver for the 80m AmRad band. Yes, I understand why you chose that - because you happened to have a suitable crystal filter available - but I strongly suggest that you re-design your receiver for a more conventional IF of something like 450 kHz. With, say, 3 of maybe 4 tuned stages at 455kHz you should be able to get adequate selectivity for ssb transmissions. If you really want a high-performance RX, have you considered double-conversion: e.g. 1st. fixed IF at 1.6 MHz followed by 2nd. fixed IF at 100 kHz.
The high IF is the cause of your low-gain. Ditch it. You don't want a "pre-amp" at the front-end.
HTH.
Al / Skywave.