Unless you plan on getting a humidifier that produces steam via an electric element energy efficiency should not even be a concern with a humidifier. They draw very little in the way of wattage. As for an EAC,IMO most people with alergies seem to feel they help.

Most homes trap enough humidity to be comfortable without humidification. Your HRV contributes to the low humidity in your home. Bringing cold outside air into your home and raising the air to comfortable levels will drop the moisture level. Cold air does not hold as much moisture as warm air. When you warm the cold air it expands and it contains a "relative" amount of moisture. Relative meaning, the percentage of moisture is dependent upon the air temperature.

What are your allergic to, not the symptoms? If you know what the allergen is then you can determine what you need in the form of filtration. Filters come with particle size limits. The smaller the particle you are filtering the more expensive the filter. Maintenance can be higher on some filters and consumables can be expensive.

Humidifiers work only when the blower in the furnace is working. I prefer the Honeywell (HE-225 or HE-265) by-pass type that uses an evaporative panel. Water runs over a panel and is dry when the house is not calling for humidity. Stay away from spray and standing water designs. If your furnace is over-sized you may not be happy with the humidifier. Steam humidifiers are expensive to operate.

Be careful with the humidity issue and the growth of mold/dust mites if you have allergens to them. They recommend you keep your humidity level around or under 40% so be mindful of not creating another problem when you humidify your whole home. Think insted of using a small humidifier in your bedroom or where you spend the majority of your time and keep a watch on the level of humidity as it seems you are doing now. The whole home electronic air cleaner is a good investment for people with allergies I have been told. I believed it and bought the Trane Clean Air Effects unit but really don't see the benefits for my son personally. I would have never bought it had I known, and certainly won't recommend it now because of the fact it produces Ozone! For anyone who has problems breathing or suffers from any type of lung issue anything that ionizes or produces ozone in any form or fashion should be avoided. The lied to me and told me it did not when I bought it and once I found out it did it was too late. The allergy doctor I work with told me the benefits may outweigh the risk since it does produce a very small amount so I am not panicking anymore. There is also a setting to lower the amount of ozone it produces and we did set it at the lowest amount. Anyway enough of that there are several nice products out there Lenox makes one, and there are plenty more out there so DO YOUR HOMEWORK before you buy and don't make the same mistake I did. Best of luck!