im afraid this gona be another flippant remark, sorry. y havent you got DSL yet? dont know where u are obviously, but in britain, the cheepest DSL ISP is UK Online, who can give you 512Kbps for GB£9.99/month which is actualy equal to or even cheeper than most dialup contract providers.
Im affraid no1 is bothering with dialup anymore, its so frustraitingly slow and archaic every1 hates it. ask me this question about 5 years ago and there would have been more point. having said that i always keep a dialup ISP on my laptop for "emergencies" lol.
The maxim possable speed on dial up is 56kbps, so it sounds like ur doing quite will as it is dude; what ever speed your connection is, weva its 56kbps or 8mbps, you will NEVER get it all the time (its cheaper for the ISP to run like that)