Connecting New Site to Head Office - RED or Another SG?

Hi Guys,

I have an SG230 at Head Office that I have 'hand crafted' all the rules, NAT, forwarding, SPAM filtering etc over the past few years and is working fine. On my local domain I run a number of vLANs and have about 100 users here and a vmWare server infrastructure etc I run a bunch of Ubiquiti switches but still have a Dell 6248 Layer 3 switch as my 'core' switch - so to speak. Hoping to replacing this with another Ubiquiti ES-48. All vLANs, Trunks, LAGs, routing etc is working fine.

I have one small remote site connection to Head Office with a Red15wi - this is working as intended.

That's the current working environment.

Now, I want to add a Branch Office that will sit about 20 staff, an RODC and 20 VOIP phones that will connect back to our PABX at Head Office. I'll be setting them up as a seperate vLAN as their will be Ubiquiti security cameras setup at that site on their own vLAN as well.

So, my question is - should I be looking at a RED device or another SG Firewall to make the connection between the two sites? 

I don't know much about the XG series and am far more comfortable with the SG's  :) 

Any tips or advice is appreciated :)

Cheers