One problem with 8 gauge or lower is the difficulty in working with it. I'm a few weeks from moving into a house with dedicated 10 gauge lines. I have easy access to the same type of wire and am thinking about experimenting.
I could wrap and solder another 10 gauge line (hot to hot, neutral to neutral, ground to ground) just in front of the connections on both ends. There would then be two solid core lines running side by side. That would leave a 7 gauge run for most of the length and 10 gauge right at the connection points (well, maybe a couple of feet on either end depending on access capability). The total run is about 25 feet from the breaker box. Is this a crazy notion? At the end, it's always "let your ears decide", but this would be a bit of work and I'd rather avoid it if it won't make any difference. Thanks.