I think a good alternative to Topo is memory-map software, particularly if you use a Windows mobile GPS-enabled smartphone or other device compatible with their stuff. They have a desktop application similar to Topo (but less buggy I think), they similarly sell per-state DVDs of maps (just over $70 per), but you can also opt to buy an upgraded version of their software that will import free USGS maps from the likes of libremap.

Their software works well on my smartphone, and I found their customer service really responsive, so I'm a happy customer. I'm also thinking of doing some hiking in England, and memory-map works with maps from some other countries, including UK Ordnance Survey maps.