I'm using an ASUS Radeon X300SE w/ 128Mb in my HTPC. I'm using the RCA video out on it to connect to my TV. Will this cause excessive strain and/or heat in my system?
More aboutdoes video extra heat
AFIAK, the type of adapter you use, analog or digital, have no direct effect to the production of heat on the card.
Unless the card has an independant DAC for the composite connection then it wont make any differenc at all. Even with an independant DAC you would need hundreds of dollars of temperature monitoring equipment to tell the difference