With a stereo only source you can biamp your speakers using a 5.1 receiver.
Recommended settings and connections:
1. Front speakers
Small (or large if you don't have a sub). Connect your mid/woofer to the fronts.
2. Center speaker
None
3. Surround speakers
Small. Connect your tweeters to the surrounds.
4. Crossover
If you don't have a sub, choose the highest setting.
If you have a sub, settings will depend on the AVRs capability. If the crossover is universal, meaning only one setting for all speakers, choose the frequency that is slightly higher than your speakers' -3dB point or according to taste. If you can set the crossover for the F, C, S separately, choose the highest setting for the surrounds.
5. Distance
Fronts and surrounds should be equal.
6. Processing/Surround mode
5 channel stereo, all channel stereo or whatever your receiver calls that setting.
ADD: you can also provide better protection for your tweeters by tweaking EQ of the Surround channels. Trim down all EQ below 1khz for less low frequency energy going to the tweeters.