From my KAV 9 days I remember getting many tips from Kaspersky user forums, search "speed" or similar. If you really want a suite, have found one you like, why dump it because of what might be a temporary problem. If your computer is very old, slow hd etc. then perhaps you feel slowdown. If at least "newer computer" side-effects should not be so dramatic as you hint. Since Kaspersky I can understand "some" slowdown but dont underestimate settings. Should be modular so dig in. I more or less changed to other AV because of what you say divided by 5. Did feel clumsy at the time but they develop new versions all the time.
You could try Norton Intenet Security Suite 2009 http://www.symantec.com/norton/internet-security
They brag about performance "Proven fastest and lightest" so are they correct or not? Worth a trial test if you want a suite.
You still need a "better" firewall if you go free AV? Could try Online-Armor http://www.tallemu.com/free-firewall-prote...n-software.html
if on 32bit. About the only firewall that satisfy my inner control freak without making me think it is too much trouble if not silly. Easy to manage and nice GUI. If it bothers you I would guess rest does as well.
Ive used Microsoft Essentials for a couple of weeks now and it runs smoothly, like Avira. You will be happy with it I think - but dont look for processes in Task Manager since ram-usage is a bit high, 70-100+mb. Possible it scales according to amount of physical ram, dont know - I have 4gb. Have some trouble seeing that being a problem unless computer is strangely configured. Some are very hysteric with AV eating resources so perhaps matter of principle. If you are one of those I would suggest NIS2009 again. Whatever free AV and free firewall you pick such a combo will probably be more resouce-intensive than Norton, at lest in Task Manager numbers.