For those of you that have an Ott Lite (or similar), is a 13-watt lamp sufficient for fly tying on a stationary desk at home, or would an 18-watt lamp be better? I can get a 13-watt Ott Lite at Costco for $39, or an 18-watt Ott Lite with the clamp/stationary base for $90. Anyone have a 13-watt lamp and wish they had the 18-watter? Any recommendations/suggestions would be appreciated!