D-Link DIR-615 :: AR9285 DWA-131 But Best Connection Is 150 Mbps

I'm using an HP G60 laptop, running Win 7 Pro x64 SP1, fully patched. I'm usually in the home office, connected to a D-Link DIR-615 router (h/w: E3, f/w: 5.10, the latest). The internal Atheros AR9285 N150 wireless adapter has never been as reliable as I'd like, so decided to purchase a USB N300 adapter. I bought a TP-Link model for $10 and started using it. For some reason, it would only connect at 150, unless I ran the router's Web interface and saved the wireless settings, even without a change, at which point I'd see 300 Mbps. However, at the next restart after hibernation, the connection with the DIR-615 would fall back to 150.

I stepped on the TP-Link USB adapter and broke it. Oops. Decided to purchase a D-Link DWA-131 (h/w: A1, f/w: 1.21, the latest) 'cause it's compact and the box says that, "For Optimal Wireless Performance +Use With Wireless N 300 Router (DIR-615)."Expected 300 Mbps, but it connected at 65. Argh. Did the trick again with the DIR-615's Web interface, and saw 150. But after restart from hibernation, back down to 65. Unable to achieve 300 Mbps, unlike the cheap-o TP-Link adapter. Router is configured according to Lycan's sticky note. Router's Wireless Status shows a signal of 39%, and the router is in the next room in a wood-framed building.Is this as good as it can be? Looks like the DWA-131 is coupla years old with no new drivers for Win 7. Ran the DSL Reports Java speed test, and seeing 18+ Mbps d/l, and 1.8 Mbps u/l, which is about average from Cox here in The OC. If I can't get a faster connection, then D-Link's claim of "optimal performance" is misleading.