I don't think it necessary to "replace" Avira as it is respected program. But as noted, all programs can, and sometimes do have false positives - that is certainly better than missing some malicious code. Therefore I don't recommend automatically removing something that is tagged. Instead, I recommend confirming it is malware and certainly the recommended use of MBAM is my first choice for a supplemental scanner.
Also, there are several reputable on-line scanners from folks like Kaspersky, Trend Micro, and PandaSoft that you can use to double check too.
If you choose to replace your anti-malware program, there are several excellent anti-malware programs to choose from, some free, some not. I recommend you chose one that performs consistently well in tests by the following respected labs: