You could have a look at a Mikrotik RB5009 or similar.
It doesn't have "hardware assist" as such, but the quad-core ARM processor will cane a gigabit of traffic easily. In addition, there is a routing optimisation called "FastTrack", which basically means firewall rules are tested against the first packet of a flow only, and the remaining packets are shunted quickly using connection tracking. Originally FastTrack was only for IPv4, but it looks like the recent v7.18 added FastTrack support for IPv6 (see
changelogs).
On an older Mikrotik hEX PoE, with a single slow MIPS core, I tested fasttrack versus non-fasttrack, and saw a 3x speed improvement with fasttrack enabled (from 300M to 900M).
Dual WAN load-balancing is a bit funky with Mikrotik: it requires some policy routing rules (flow marking) or equal-cost multipath. Again, this used to be something you could only do with IPv4; it could well now work with IPv6, but I've not tested it.
IMO, the main downside of Mikrotik is that there is no "long term support" branch of their v7 software, i.e. no "bug fixes only" branch. They're constantly adding new features, so if you upgrade to a newer version to fix problem X, you may also introduce unexpected problem Y. This is why my main router, RB4011, still runs v6. But the newer products like the RB5009 only support v7.
Aside: there are some models of Mikrotik which do full
layer 3 hardware offloading. They are mostly switches though. There are a couple of high-end routers which support it, such as the CCR2116-12G-4S+ (RRP $995) but I suspect it doesn't work with PPPoE anyway.