Or go sealed, you can put an alpha 8 in a 0.5 cuft sealed box and it isn't peaky (according to boxplot). Less bass but no big bump ...
And if the amp allows for it you can set the speaker to "small" so bass is diverted to the L and R channels. Modern amps may allow even more precise bass management.
Also keep in mind that you can alter the dimension of the cabinet to whatever will fit in the space available. The box is so small the resonances will be very high and don't matter too much (maybe Wayne can verify).
You might have trouble finding matching KSN1038s. Depending on how old the others are ... I recall Wayne saying that they switched factories or companies and the quality wasn't the same.