Regarding LVS--if you build an LVS-DR cluster you can run both Pound and LVS alongside each other on the same box. LVS doesn't do layer 7 load balancing so it won't be able to distribute traffic based on session information (HTTP header info). For large file transfers like you describe, however, LVS-DR would be a good choice so you can route the packets directly back to the client computer (not through the load balancer) which is what LVS-DR is all about.

The LVS HOWTO is an excellent resource, <begin plug> you may also want to check out my book on the subject called, "The Linux Enterprise Cluster" <end plug>.