What's wrong with eagle?Its updated regulary, can do 80mmx100mm boards with free version, gets easier to use with practice.Has lots of parts libraries, and can design your own parts.Can get a lot of stuff on a 80x100mm board.
Check out DipTrace. It's fugly though, running on OSX. But I think it's a worthy contender/upgrade/step-up from Eagle.
Heatsink pads - I fake those in eagle by giving the polygon pads the same name as the signal on the board drawing, then you can overlap them. Will get overlap errors when you run the DRC that you can ignore.
Kicad is mentioned regularly.Or that toy, fritzing. Have never seen a good schematic posted from that.
Why don't you just edit the library, clone the part, but make the smd pads bigger on the new clone. Another technique, if there's nothing behind, you can put another heatsink pad in the bottom copper layer, and use several vias to connect/bridge the upper and bottom pads. Also order your boards as 2oz copper.