1. Don't download 1.5 GB+ files, moron.
2. Banswidth is split between PCs. How many others are active on the router?
3. Put some units with your number... i have no idea what 10-20 download is.
4. If you have 20-50 (assuming 'Kb/s' or 'Kbps') Upload... it's time for a new ISP buddy.