A router that meets most of your requirements would be a NETGEAR N750 Wireless Dual Band Gigabit Router (WNDR4000):

It currently supports (assumes latest firmwar):
- 4-port switch (integrated) - EN, Fast EN, Gigabit EN
- Wireless: IEEE 802.11b, IEEE 802.11a, IEEE 802.11g, IEEE 802.11n
- PPPoA & PPPoE
- Port forwarding
- USB Sharing via dedicated port
- Both private and guest wireless networks
- Isolation modes
I have deloyed around 15 of these routers and they are stable and offer a host of features at a fair price point (prices range from $145.00 to $170.00 online).
I say most because fits most of your requirements SANS the DD-WRT. I can point you to this router from ASUS RT-N16 Wireless Router:

This router does support all your requirments with a caveat. I can not vouch for how stable it is as I have never deployed one. I will be deploying one in 3 days so I will update this question with my opinion. The price point is far cheaper than they Netgear WNDR4000 at $80.00 most places online.