What more important?

Okay, so here is an update. I went to the hardware store today and got two daylight T12 40 Watt bulbs with 6500K ratings. I took out the expensive bulbs that I got from Petsmart (almost $20 a piece) and I am going to return them for store credit. I should get about $50 credit.

So, with that in mind, I think I have my lighting right now and I am getting ready to order some low light plants from Mgamer tonight to increase the number of plants in my 55 gallon from 2 to about 8. So, the only thing left to do is to figure out what I need to use my $50 credit towards. Here is what I think I need to do:

1. Upgrade my filter from Topfin 60 to a Penguin 400 (about $50)

2. Buy some flourite to layer the bottom of my tank with and put my existing substrate on top of it.

Which one of these moves would benefit my new stock of plants the most? Or any other ideas on what to get? Thanks!

My existing substrate is medium to large rock.

Okay, well I went into the LFS and traded in the expensive (ripoff) lights they sold me and got flourite and another Topfin 60 (300 gph) for my 55 gallon tank. That gives my filtration over a 10 times turnover rate per hour so I feel pretty good about that because it was on sale.

My next question is: Does flourite mess with water chemistry any? Are there any precautions I should take before adding it to the tank aside from thoroughly rinsing it off?

also, now I have 4 filter cartridges in my tank. I was think about two that are full of activated carbon and the other two full of ammo chips. Is that a good idea?