Filter... If you don't wont to go with the heated version of the Eheim then the 2026 will be great. Try Big Als
they have the best prices on a lot of equipment.
Lights... I myself prefer Coralife fixtures, but have never used the Orbit fixture. Marine & Reef
have good prices on light fixtures and is where I buy mine from.
C02... You can buy or make the individual components needed for a pressurized system cheaper than what Dr. Fosters is selling theirs for... Look at this link http://sammyxp.tripod.com/html/id23.html