Or...if you just have to try a high IQ lens, maybe get the pancake 40. Lots of folks with lots of L glass are saying great things about that lens and the posted shots seem to back up the talk. I've seen it for $149 on sale.
+1 on this suggestion. The main gripe about the EF 40mm lens has been stronger vignetting when wide open on a full frame camera but that "issue" is mostly alleviated by using a crop sensor camera. Also, get the kit with the lens. Really, give it a go and learn the equipment. See if this is what you want to do and what areas of photography excite you. See what images you can get out of the basic equipment before an upgrade to high end glass. Only then can you do a comparison of images from basic and expensive glass with subject material that excites you and come to a correct conclusion if the expensive glass is worth it FOR YOU.
If you do not mind getting used equipment, the full frame recommendation of the 5D classic body is a good one as you can get them cheaper than a new Rebel body.