If you go with either of those you'll have more than enough light that the glass top won't make a difference.

I'm pretty sure you can't link stores, so I'll send you a link via PM to the Odyssea fixtures.

Is the $30 a ladder type looking thing? Those are semi-DIY co2 systems. With 5wpg they won't produce enough steady co2 to keep algae in check. Look into a regulator and a pressurised cansister of co2. You can rent a 2lb canister for like $4 per month from your local welding shop. Or, you can buy it for around $60-$80. So, all in all, the co2 will cost about $150ish. As for making co2 external...the only ways I know of is with a sump or if you inject it into your filters impeller, but then you'll be buying new impellers every six months or so. If you're thinking they just don't look all that great internal search for glass bell difusers. These look awesome most people think.

You could just get a pane of glass cut to size at your hardware store that doesn't have that middle divider thingie orrrrrrr give an open tank a try