ladder type vr as pre for aleph

[jrsun]

I temped to build a passive preamp for my Aleph 2 by using a 10K ladder type VR but have the following questions

1. the ladder VR has constant input Z, i.e. Ri + Rg, but how about the output impedance ? Rg ?
2. Aleph has low imput Z, 25K, if the Z ratio is low, what do I suffer ?
Thanks !