So far as I remember, you are the first in this forum who justifies the use of i7 so eloquently. I definitely think you should purchase i7 CPU. From the beginning, it might be helpful to concede that (in contrast to our intuition) it is really challenging to settle with a concrete rig configuration because there are so many points to be factored into solving the problem.
Is there anything about that build you wish you had done differently?
Yes, I would have not bought a discrete GPU because I can't seem to get interested in playing games any more. I also think it is more sensible to go with a Mini-ITX system nowadays because Nividia will be churning out incredibly power-efficient graphics cards based on 20nm process sooner or later and all Haswell CPUs including the top-notch model such as i7-4770K can be made to be reasonably quiet in Mini-ITX chassis.
One of the things that was pushing me toward a small case is that my wife hated my old large chassis. When the fans kicked in, the system was so loud it would send our pets into a panic. If going larger is going to help acoustically, I'm all for it.
When I saw this, I realized that you have a completely different threshold for noise/silent computing. What I mean by quiet computing is literally "dead silent" one. For instance, the CPU temperature of my main rig with i5-4430 in mATX chassis stays around only 47 Celsius under heavy load where the fan speed is merely 600 rpm. It is a utterly extremely silent configuration for those who are massively "paranoid" for noises, which in turn implies you can still stick with Mini-ITX chassis. On the other hand, you must be aware that the official TDPs of i7 and i5 CPUs are shenanigans. For example, my i5-4430 consumes about 40W (as CoreTemp says) under full load, which is considerably lower than what is reported to be consumed by i7-4770K.
If you take into account all the possible scenarios (e.g., your wife's preference to small chassis, possibility for a discrete GPU, and avoiding your pet's panicking), I reckon that it is virtually impossible to determine your next rig. In any case, I strongly recommend you to opt for Asrock Z87E-ITX (or a bit cheaper H87E-ITX) because Asrock Haswell motherboards provide absolutely fantastic and flexible BIOS fan control functionality with "true" PWM fan headers, as opposed to ASUS.
Though I can't advise you for all possible combinatorial outcomes (I'm just a layman user and not necessarily well versed in all recent hardware trends and my job has nothing to do with computer hardware), if you are fine with or can tolerate (i) some breeze-like whoosh of airflow arising from the CPU cooler fan under full load and (ii) complete silence under idle state, I conjecture that you will be definitely satisfied with Lian Li PC-Q27 along with Scythe Big Shuriken 2 (CPU cooler) which nicely fits into PC-Q27. As for PSU, I would just opt for Corsair RM450, which I've installed and used in my office PC very satisfactorily. I think it is also an idea to experiment with a Pico-PSU but I seem to have seen some posts about electrical noise of Pico-PSUs. I'm massively leaning towards this option of smallest Mini-ITX chassis for standard PSU because you can eliminate even the non-disturbing whoosh airflow of CPU cooler fan simply by underclocking (which I do in my office for i7-2600) if you have to, e.g., during nights. Lastly, you'd better aware that Haswell CPUs are more than manageable in terms of CPU cooler fan noise, particularly considering that your current rig seems to be quite outdated (to the extent of incurring panicking of your pet). As a digression, as you can see from my signature, I have Lian Li PC-Q11A which is in silver color in our living room and my family seems to have a liking to its color and aluminum texture. You might want to try PC-Q27 Silver.
If you crave for a utterly silent rig irrespecitive of CPU load that can accommodate multiple-slot discrete graphics cards, there are many mATX chassis or Mini-ITX chassis bigger than PC-Q27.