need help vlan

Hi,

 

Our current config:

1-cisco 2924, 1-cisco 2950, 1-Dell 5324, 1-Dell 5224. we dont stack them just connect every switches to 5224 where all of my servers connected.

We are adding 25 voip mitel phone, the seller told us that need to buy any switch, we don't need vlan and it won't affect the current network. Now few days from installation day, they told me that we will need to buy layer 3 device for vlan. The problem is with the user's pc that has ip-phone, the way it connected is from switch it goes to phone (vlan2)---go to pc(vlan1). with this config do I need PowerConnect 6000 series or i can use 3448p that we just bought?

Also the voip server (will be connected to new switch) is on vlan2 and the gateway is on dell 5224 (all vlan1/default)

 

Thanks,