Well, in the 500 plus category there's quite a handful of worthy candidates for the money. I had a chance to compare 3 of them back to back. They are the KRK RP-5s, M-audio BX5a and the Alesis M1 Active 520. Here are my thoughts on each of them.
Firstly the KRKs. This was the first pair that I heard. Nice smooth sound with a tight low end. It definitely brought life to the electronic breakbeat track, which was the source material for this audition. Bass was tight and punchy. Mids and highs smooth. A nice sound that I liked.
Next, the M-audio. The mids had more 'presence' in this speaker, at times sounding rather harsh. Bass was tight but i felt that it lacked 'punch'. Overall, not a comfortable listen.
Lastly, the Alesis. They have the same 'character' as the M-audios. In other words, they have that same 'presence' in the mids but smoother sound overall.
Well, these are my thoughts on the 3 speaker that I auditioned. However, the comments are based on my personal thoughts on the quick audition session I had and not a professional test of any sort.
Haven't heard the Tapcos yet. Perhaps fibredrive would kindly share his opinions on the 3 speakers he mentioned?