Hi,
When you say the temps on the basking "side" are you referring to the actual basking spot, directly under the light? Are you using a digital with probe, laying the probe exactly where beardie basks, to gauge temps? If not, then you probably aren't getting accurate basking temps. I would certainly get a digital with probe (if you're not already using one that is), before making any decisions. You will certainly want to know the exact basking temp UNDER THE LIGHT before proceeding. I won't steer you away from using a MVB. We use one and it's been WONDERFUL for beardie, however, if it's more heat you're after, perhaps you simply need a higher wattage basking light? What wattage basking light are you using, and what type (basking specific, household incandescent, household flood)? What are you using for UVB (type and brand) btw?
The PowerSun is a 'good' bulb. That said, the PowerSun is not as strong as some in terms of UVB
and heat. Honestly, for a few bucks more you can get a TRex MVB,
http://www.petmountain.com/product/reptile-heat-bulbs/503619/t-rex-active-uv-heat-flood-spot-lamps.html which emits much stronger UVB, and throws out more heat than the PowerSun.
To note, for a MVB, your tank should be 40 gallons or larger. For a 100w (40 to 55-60 gallon tank), the bulb should be
no closer than 12 inches from beardie. For a 160w (75 gallon and up),
no closer than 18 inches. You will have to use calcium dust withOUT D3,
http://www.petmountain.com/product/reptile-health/105556/rep-cal-ultrafine-calcium-without-vitamin-d3.html Also, VERY important: these bulbs have a burn in period of a few days. You will want to check temps OFTEN during the first four or so days and adjust your bulb accordingly. We had perfect basking temps on the first day at 12+ inches. By the 3rd day, they were too high and we had to adjust the bulb up. By the fourth day, things leveled off and we ended up with a distance of 14-15 inches from bulb to beardie basking spot. Remember, when checking temps, to place the probe DIRECTLY under the light, exactly where beardie basks and
leave the probe for 45 minutes BEFORE reading the temp.
Hope this helps! Best of luck in whatever you decide.
The best,
Em