I've got to agree with jim on this, I have no complaints on range with the Almond+. I didn't do any before & after tests, so I don't have specific numbers, but my perception is its range is at least as good as my AirPort Extreme (Dual-Band 802.11n model), if not better. I haven't tried the 802.11ac mode as I don't have any ac devices yet.
You might want to try the Wireless Diagnostics app built in to Mac OS X 10.9 to check the signal strength between your AirPort Extreme and the Almond+. You can access that app by doing the following: Hold down the option key while clicking on the AirPort icon in the menu bar, select Open Wireless Diagnostics..., enter your admin password to allow Wireless Diagnostics to run, DO NOT click the Continue button as you don't actually want to run the diagnostics, select Utilities from the Windows menu when the Wireless Diagnostics app opens, then click the Performance tab. That will give you a realtime graph of your wireless signal and you can compare the two devices. If the Almond+ shows a significant different I'd suggest your contact Securifi for a replacement.