Hi mr4stringz,
Sub £300 is possible for new analogue mixers matching what you appear to be saying.
There appears to be a contradiction in what you write "enough oomph" requirement for a mixer. What model speakers do you have?
One I have used for vocals with nice microphones and small gigs is the Mackie DFX 6 mixer (now discontinued) which also has reverb. Whilst you have not stated that you require reverb, many singers appear to require it. I own a few different mixers.
Suggestions Within your budget, have effects and are New:
Soundcraft EFX8
Soundcraft Signature 10
Mackie ProFX12 V2 Mixer
Mackie ProFX8 V2 Mixer
A little over Budget and New:
Soundcraft Signature 12
Soundcraft Signature 12MTK
At this price point I find these to be better than the A&H 'Zed' range which having tried, avoid when better are available.
Hope this helps. To go further, I could do with knowing what the speakers are.