A few thoughts . . . Things a D70 can do that you might not know (or haven’t thought important). . .
1. The D70 can run any lens vs the limited capability of the D40 – you know that already.
2. The D70 has the ability to be a master flash trigger for the Nikon creative lighting system. This is a big deal if you plan on doing off camera flash, for example fly tying shots or product shots that are often discussed/shown here. That alone is a reason to get the D70.
3. The D70 processes pictures faster than D40; not much but still helpful.
4. The D70 requires less menu manipulation to change manual settings – this allows for faster manipulation during “must get” shots (i.e. on the water shots of trophy fish).
5. The sigma wide angle lenses typically range from $200-$400, so depending on the lens he is including that might be a good investment. However, if it is the Sigma 18-50 that is not a high quality glass and goes for less than $100 on ebay; make sure you know which one is on the body.
overall, with all the upcoming Nikon body changes you might be better off waiting until you know exactly what you need, but that is a personal thing and tough to define.