Higher frequency sounds are more prone to disruption by putting things in the way, so if you're going to block the tombstones I wouldn't use components. Are you keeping the factory HU? I don't know how it crosses over the signal, but if it's a full signal to all channels I see no reason why you shouldn't keep the factory tweeters in there and run coaxials in the pods.
I wouldn't use the db651s speakers though, there's no need to put slimline units in the front pods. If you want Polks use the standard db651, you'll get a bit more power from them and I think they're a little cheaper.