There is a problem with all the benchmarks out there. They don't appear to translate well to what an average user uses. They seem to be built around the curiosity of: (a) gamers, (b) high definition enthusiasts, and (c) hardware enthusiasts interested in synthetic benchmarks to chase.
Our hypothetical average user has no idea what cache is. The average user confuses memory and storage, thinks Windows comes with Office, and thinks POP is a beverage. They are not the intended audience for tech sites.
I agree - synthetics do not translate into real-world performance. Most tech sites use canned benchmarks because it's a convenient way to compare hardware. But others don't - for example, [H]ardOCP eschews canned benchmarks and instead actually plays games to test hardware. They report on the gaming experience. They're a PC gaming enthusiast site, and their tests translate perfectly into what their intended audience does.
Here is what I use. Typically with a fair number of windows open at the same time:
Browsers (Chrome and Foxfire and sometimes MS internet explorer)
Windows Explorer (I use it a lot and it sometimes has pauses while it waits for my HDD to be doing something - a black edition 1T WD)
Word processing (MS Office & Open Office - both can sometimes be slow in launching a file through Windows explorer)
Scanning software (bloated third party, bloated Brother, and extremely bloated HP software)
Anti-Virus (AVG and sometimes Avira - I have switched portions of them off because they can drain system resources)
X1 desktop search engine (when it is indexing files it loads the system up similarly to the Anti-virus software)
iDrive backup software (when it is backing up the system it loads the system similarly to the Anti-virus software)
PDF (Foxit PDF reader, Adobe PDF reader and CoolPDF printer)
farstone cloning/backup software
I'd say you typify the average office PC user. Most of your slowdowns sound like I/O issues, and will not be helped by larger CPU cache. The benchmarks related to cache were picked because they are CPU-intensive. Ie, the disks are waiting for the CPU to complete whatever it's doing. I don't think any of your aps behave this way.
I would get rid of AVG. AVG used to be the light-weight AV of choice, but has become bloated and slow over the past few years. I dropped AVG as soon as they started with the advert pop-ups (8? 8.5?). I use MS Security Essentials, which has been terrific to date. It's lightweight, fast, and well-reviewed.
Lots of windows, browsers and browser tabs will eat RAM. If you're using a 64-bit OS, don't be afraid to go a little nuts on RAM. If you're not overclocking, don't worry about memory clock speed. But pay attention to latencies. Get low-latency JDEC-compliant RAM, and lots of it.
The rest of your issues sound like
1) poor software coding
2) I/O limitations of your mechanical disks
I am building a new computer. I have a Zotac mini-ITX board. I have a Lian Li Q07 case. I was going to put a Q9550 CPU in it. But I want to power it with ElectroDacus's winmate PSU system. I am not fully comfortable using it to power the Q9550.
So I am looking for a less power hungry substitute 775 cpu. The published benchmarks do not seem to be helpful.
The three articles I linked to were a response to your question: "More cache, what good is it?", and is no help for the power question. The least power-hungy LGA775 CPU right now is probably one of the Wolfdale Celerons
(xbit labs) precisely because they have less cache. I have an E3300 + G41 board in my HTPC, and it consumes no more power than the previous AMD 4050e (45W TDP) + 740G/SB700 system it replaced.
So I don't think this 775 system is going to be a speed upgrade to the Clarkdale system. But I don't want a sluggish system either.
So what CPU do I select? What is the tradeoffo in Cache and in GHz for my uses?
I don't think the LGA775 system will be faster than the Clarkdale system either. Most of your applications are not heavily threaded, so the Q9550's extra cores don't benefit you. Your aps look I/O bound. Faced with that I'd spend on a fast SSD and - to a lesser extent - high CPU clock speed for good single-threaded performance.