FiiO A3 is a good choice for an inexpensive headphone amp. It's portable, so you'd need to charge the battery, or possibly just leave it plugged into USB. You'd still need your E-DAC though, which is fine. It's just a headphone amp, unlike the E10K which is a DAC/amp. Only one input though, so you'd need to run another splitter cable in order to plug both E-DAC and input from the Humax box into the A3.
Perfectly workable option though.
Just had a look at the FiiO Q1. I'm not familiar with that as it's one of FiiO's newer products. Looking a bit closer; it is similar to the A3, but a DAC/amp. Looks like the amp puts out less power than the A3 though. While looking to see if this would be a suitable choice, I found a question on FiiO's forums from someone asking about using the DT770's with the Q1. A FiiO rep said the Q1 may not have enough for those headphones. As I said in a previous post though, FiiO are conservative when it comes to the output power of their headphone amps. Certainly a good thing and better than claims of being able to drive 600 Ohm headphones, when it can't; like we see from some gaming audio product manufacturers.
Read a review on head-fi of the Q1, from someone who does very good thorough reviews and he mentions that while using pair of Sennheiser HD600's, which he thought the Q1 did a commendable job with. If it can do fine with the HD600/650, it shouldn't have any trouble with the DT770.
The Q1 a better option than the A3 in my opinion, as it has 2 inputs; DAC via USB and 3.5mm analogue. Costs slightly more, but only about £10 extra.
So far then, we have; Creative G5, FiiO A3 or Q1 and FX-Audio X6. All are workable solutions. G5 is double or more the cost of the others, but I'm not certain it's £120 well spent if you have no use for the other features it has over the cheaper options. Technically, you'd be paying twice as much or more than one of the others that will do the same thing. G5 has a better DAC, but whether that will be noticeable and worth the extra is uncertain.