The 868L should be comparable to the 655 on the 2.4GHz band. The 655 does not have a 5Ghz band so there is a difference there. The 868L's raw routing throughput is also much better. In order to take advantage of AC Smartbeam you need an AC adapter. From a 2.4GHz perspective, the 868L in all locations should provide better throughput than the 655.
In other words, if you ran a wireless filecopy from a laptop 10 feet away to a wired PC, the file should transfer faster than the 655. This should also be the case at further distances as well. To complicate the matter even more, the results may not be significantly better if say you are using a wireless G adapter or a low cost N150 adapter because the bottleneck is the adapter.
When it comes to wireless technology, your mileage will vary. I've put multiple routers against eachother and depending on where I am testing, the results vary except when comparing a low end router against a high end, the results are then fairly black and white.
If your goal is to get wireless coverage in 1-2 areas within the home on the 2.4 GHz band, DAP-1320's may do the trick. Small, affordable and does the job if you are just looking for signal strength.