I have absolutely no clue if this will work as I haven't tested this, and I have NO idea which drivers were added to beta 6, but I'm going to make a recommendation anyway.
Working fine for me on 5.0rc7, haven't upgraded to anything later yet, but later versions should also work. Stock R210 with on board NICs (Broadcom). Dell's Intel option (dual PT gig should also work, that card is based on the 82576 chipset, which is supported).