I have an existing router; replace it with the the Time Capsule or just connect the TC to it?

I have an existing router, a Netgear N900 (not AC, just N). Should I replace it with the the Time Capsule or just connect the TC to a free Output Ethernet on the Netgear?

Either way will work and either way I'll get the higher speed (AC) of the Time Capsule. Ideally I should remove and retire the Netgear and use the TC only. But, the Netgear is perfectly usable still.

Current configuration is, AT&T DSL modem in bridge mode => Netgear N900 => main router/Wap for house. So what's probably best in the long run is replace the Netgear with the TC...and this question is probably unnecessary since it's been answered generally before.

Before I go to the hassle of switching just want to confirm it's best, or, perhaps confirm a full replacement offers no advantages.