Blu Ray will give you full 1080p, which is better than any other type of tv-upscaler, receiver, dvd player, etc etc.
Now some TVs, Receivers, and Up-Scaling DVD players will upscale lower outputs (480i, 480p, etc) to 720p/1080i/1080p to the best of their abilities. However, it will not match the quality of a blu-ray player.
I am sure your tv you just bought has an internal upscaler in the tv that will upscale your video to its native resolution, therefore the importance having a receiver to upscale isn't very important, UNLESS it does a noticeably better job than your TV.