Most bang for the buck?

I wasn't sure which category to post this under....but here goes:

I will be doing one of the 4 upgrades listed below in my life (5yr plan). I will possibly do all 4 eventually. I invite input from the knowledgeable group as to which would provide the biggest improvement overall.

My electronics are: HCA-2, Carver Sunfire preamp, Music Hall 25 Mod +, Epicure 3.0 way cabinets that have completely redsigned drivers and crossover from Meniscus boys with a pair of Vandersteen 2wq's.
1. Biamping the mids and highs, or left right? with another HCA-2
2. Getting a power conditioner
3. Upgrading to a PCA-2
4. Modding the HCA.
What about room treatments and dedicatd AC lines? AC power conditioning can be accomplished without buying an expensive conditioner. Of your options, I would go for gettig the HCA upgraded. The amp sounds great but has limits in the stock form. Oh yeah, buy better recorded CDs also.

happy Listening.
>>and dedicatd AC lines? AC power conditioning can be accomplished without buying an expensive conditioner.<<

Dedicated AC lines are no guarantee of clean power. Some areas of the country have hideously noisy and poor quality power in which case a dedicated line is basically useless. A good power conditioner is essential IMO.
If you have good equipment, the power supply will take care of any noise on the lines.
Now, if your particular choice in electronics is a bit skimpy in that area, yes, a power conditioner can help.
I absolutely agree with power conditioning. If dedicated lines can be done as well then include them, but not to the exclusion of a good power conditioner. The other changes will add incremental improvements, but if you don't take care of all the major links in the chain first then those mods won't be as effective. Also be sure to include cables, if you haven't already done so. :o)
I went all Signal cable for wires and connects.
How well have your room acoustics been addressed? This will give you the most bang for buck if you haven't already done so. Also a Behringer DEQ 2496 and the ECM 8000 mike for 300 bucks can work wonders too. Amplitude variations affect the sound quality quite profoundly and in any high end system need to be addressed.