Looks great! I have the same tank with the 500. Looks like we both use up every available spot in our sump and cabinet!!! Is that DOS for water changes?I installed the 500 on my RSR XL300 two nights ago. Modifying the sump certainly wasn't fun but it wasn't too difficult. I just took my time and was super careful. I couldn't find the sump modification kit anywhere but I found a really small Dewalt utility knife at Home Depot and was able to make that work fairly well.
It definitely takes up more space in the sump than what I'd like but it has already made a big difference on the clarity of the water in my tank. I'm looking forward to seeing the long term results.