FireFox/Chrome in KVM does SSE passthrough helps

Question

I working on an Ubuntu based remote desktop environment which would run Firefox/Chrome in a KVM virtualmachine but the performance is far from "good" even compared to a laptop so I have tried CPU passthrough to present all the available flags for the VM guest like SSE2, SSE4.

Did anyone achieve performance gain by doing so with these softwares in a VM or it does not matter even if I use a generic kvm processor inside?

  <blkiotune>
    <weight>100</weight>
  </blkiotune>
  <vcpu placement='static'>8</vcpu>
  <os>
    <type arch='x86_64' machine='pc-1.1'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <cpu mode='host-passthrough'>
  </cpu>