Cisco Switching/Routing :: SG300 Network Setup For Voice And Other VLANs?

I have spent several days tearing my hair out trying to properly configure our small business switch (SG300-10p) for voice. The phones are a relatively new addition and will replace old POTS phones.Our network consists of a 1941 ISR router, the SG300-10P switch, a mac server (handing DHCP, DNS, AFP), 4 client desktops and 4 SGA525G2 IP phones. The router, server, desktops and phones all have their own connection to the switch and the second data ports on the back of the IP phones are not used. We do not have any unified comms devices for voice. Our VOIP solution is hosted by a local SIP provider, and each phone independently registers with the provider's SIP proxy over the internet.

Left almost to it’s own devices (or presumably flat, default settings on VLAN 1), this whole setup works just great. We can TFTP files, make and receive calls, and do all the usual XML stuff. Calls are crystal clear. Even the localisation and directory works. However, I’ve been told several times that to ensure good quality on VOIP calls during periods of busy traffic, I should set up some form of QoS. A Voice VLAN on the switch, I was told, is the best way to do this as it automagically gives priority to the whole voice VLAN over the normal data VLAN.

I have followed instructions in numerous manuals, articles and guides, and have managed to create the Voice VLAN, both manually and automatically (I can watch Smartport detect the phones and see the Auto Voice VLAN add the ports to the VLAN as I connect them). The trouble is, as soon as this happens, the phones lose connectivity with the rest of the network, including the DNS server and the router, and therefore the internet, causing them to lose registration with the SIP service.

I tried adding the server and router ports to the Voice VLAN and tweaking every possible combination of tagged, untagged, excluded, trunk, access, general and PVID settings I can think of (by the way, I have no idea what any of those mean). The switch is in Layer 2 mode, but adding the port connected to the router to all the VLANs does not result in internet connectivity to the phones. I have told the phones to tag frames with the VLAN ID and told them not to. I have tried upgrading firmware and I have rebooted the switch so many times I'm tired of those wretched little flashing lights.
 
Nothing seems to work. And so I am stuck with everything on VLAN 1. My most recent thought is that the 1941 needs to know about the Voice VLAN (I checked CDP and it knows about the switch), but I’m reluctant to start messing with the router config when this is our production network, at least without knowing what I'm doing. I don’t even know if QoS applies when a Voice VLAN is not set up and we're on VLAN 1, some articles say yes, others say no. And when it is set up right, how does that priority transfer to the router? I’ve looked in the router manual and config options and found something called 802.1Q, but I have no idea what it is, how it works or even if it applies to our situation. Can I forgo VLANs altogether and use QoS some other way, perhaps?I have googled enough to cobble together our setup in IOS up until now. Ideally, I would still like to be able to ssh or https into each device (as I do now) for management, and I’ve read about setting up a another VLAN for config, monitoring etc, but I guess that would mean routing between VLANs in Layer 3.