New 50 Gallon, so confused!

I have recently received a new 50 gallon glass tank for Christmas.
Merry Christmas to me. I have kept smaller sal****er tanks for several
years (3-12 gallon Eclipses) and have had great success. However, I am
lost with this newest endeavor. I have read volumes of information now
in attempt to find the best choice for a filtration system for the new
tank. I am so confused! Any help that could be offered would be greatly
apprectiated.

I plan on keeping 20-30 lbs of live rock, assorted inverts (shrimp,
urchins, crabs, snails, etc...), and likely seahorses. The seahorses
are the big decision, I currently have several seahorse tanks and they
limit the choice of other creatures in the tank. I have not yet decided
whether or not to do them, but regardless I still need filtration. No
matter what I put in the tank, it will not consist of large amounts of
fish, but instead will be heavier on invertebrates.

I had originally thought a sump system would be the best, but I now
have no idea! Another important factor is my limited budget. As a
college student working as a part-time chemistry tutor I am not exactly
loaded. The LFS's have been little help in helping me find effective
yet inexpensive solutions (go figure). I am totally open to any
suggestions from those of you who are more experienced in the aquatic
arts then myself.

Here is what I am planning on so far:
Crushed Argonite (2 inches) or Sugar Sand Bed (1.5 inches)
20-30 lbs live rock (transferred from other tanks and newly purchased)
Ultra Compact Lighting

Please Help.